diff --git a/composer.json b/composer.json
index 166886f7..024c8e95 100755
--- a/composer.json
+++ b/composer.json
@@ -24,15 +24,20 @@
         "myclabs/php-enum": "^1.7"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.5.1",
+        "phpunit/phpunit": "^10.5",
         "mockery/mockery": "^1.2",
-        "infection/infection": "^0.13.4",
-        "phan/phan": "^2.4",
+        "infection/infection": ">=0.13.4",
+        "phan/phan": ">=2.4",
         "friendsofphp/php-cs-fixer": "^2.16"
     },
     "autoload": {
         "psr-4": { 
         	"PHPHtmlParser\\": "src/PHPHtmlParser"
        	}
+    },
+    "config": {
+        "allow-plugins": {
+            "infection/extension-installer": true
+        }
     }
 }
diff --git a/src/PHPHtmlParser/DTO/Selector/RuleDTO.php b/src/PHPHtmlParser/DTO/Selector/RuleDTO.php
index 5299e3a0..6a3b0b3c 100644
--- a/src/PHPHtmlParser/DTO/Selector/RuleDTO.php
+++ b/src/PHPHtmlParser/DTO/Selector/RuleDTO.php
@@ -36,6 +36,11 @@ final class RuleDTO
      */
     private $alterNext;
 
+    /**
+     * @var bool
+     */
+    private $isNthOfType;
+
     private function __construct(array $values)
     {
         $this->tag = $values['tag'];
@@ -44,21 +49,23 @@ private function __construct(array $values)
         $this->value = $values['value'];
         $this->noKey = $values['noKey'];
         $this->alterNext = $values['alterNext'];
+        $this->isNthOfType = $values['isNthOfType'];
     }
 
     /**
      * @param string|array|null $key
      * @param string|array|null $value
      */
-    public static function makeFromPrimitives(string $tag, string $operator, $key, $value, bool $noKey, bool $alterNext): RuleDTO
+    public static function makeFromPrimitives(string $tag, string $operator, $key, $value, bool $noKey, bool $alterNext, bool $isNthOfType = false): RuleDTO
     {
         return new RuleDTO([
-            'tag'       => $tag,
-            'operator'  => $operator,
-            'key'       => $key,
-            'value'     => $value,
-            'noKey'     => $noKey,
-            'alterNext' => $alterNext,
+            'tag'         => $tag,
+            'operator'    => $operator,
+            'key'         => $key,
+            'value'       => $value,
+            'noKey'       => $noKey,
+            'alterNext'   => $alterNext,
+            'isNthOfType' => $isNthOfType
         ]);
     }
 
@@ -97,4 +104,9 @@ public function isAlterNext(): bool
     {
         return $this->alterNext;
     }
+
+    public function isNthOfType(): bool
+    {
+        return $this->isNthOfType;
+    }
 }
diff --git a/src/PHPHtmlParser/Dom/Node/InnerNode.php b/src/PHPHtmlParser/Dom/Node/InnerNode.php
index 448057a7..2b9fb305 100644
--- a/src/PHPHtmlParser/Dom/Node/InnerNode.php
+++ b/src/PHPHtmlParser/Dom/Node/InnerNode.php
@@ -100,6 +100,25 @@ public function countChildren(): int
         return \count($this->children);
     }
 
+    public function childNodes(): array
+    {
+        return $this->children;
+    }
+
+    public function childElements(): array
+    {
+        return array_values(array_filter($this->getChildren(), function ($el) {
+            return !$el->isTextNode();
+        }));
+    }
+
+    public function childElementsOfType(string $tag): array
+    {
+        return array_values(array_filter($this->getChildren(), function ($el) use ($tag) {
+            return $el instanceof HtmlNode && $el->getTag()->name() == $tag;
+        }));
+    }
+
     /**
      * Adds a child node to this node and returns the id of the child for this
      * parent.
diff --git a/src/PHPHtmlParser/Selector/Parser.php b/src/PHPHtmlParser/Selector/Parser.php
index 4643c467..3f1be13b 100755
--- a/src/PHPHtmlParser/Selector/Parser.php
+++ b/src/PHPHtmlParser/Selector/Parser.php
@@ -19,7 +19,7 @@ class Parser implements ParserInterface
      *
      * @var string
      */
-    private $pattern = "/([\w\-:\*>]*)(?:\#([\w\-]+)|\.([\w\.\-]+))?(?:\[@?(!?[\w\-:]+)(?:([!*^$]?=)[\"']?(.*?)[\"']?)?\])?([\/, ]+)/is";
+    private $pattern = "/([\w:*>+~-]*(?:\([\w\d]+\))?)(?:#([\w-]+)|\.([\w\.-]+))?(?:\[@?(!?[\w:-]+)(?:([!*^$]?=)[\"']?(.*?)[\"']?)?\])?([\/, ]+)/is";
 
     /**
      * Parses the selector string.
@@ -40,9 +40,10 @@ public function parseSelectorString(string $selector): ParsedSelectorCollectionD
             $value = null;
             $noKey = false;
             $alterNext = false;
+            $isNthOfType = false;
 
             // check for elements that alter the behavior of the next element
-            if ($tag == '>') {
+            if ($tag == '>' || $tag == '+' || $tag == '~') {
                 $alterNext = true;
             }
 
@@ -58,11 +59,41 @@ public function parseSelectorString(string $selector): ParsedSelectorCollectionD
                 $value = \explode('.', $match[3]);
             }
 
+            // check for pseudoclass selector
+            if (strpos($match[0], ':') !== false) {
+                $pos = strpos($match[0], ':');
+                $key = 'pseudoclass';
+                $tag = $pos > 0 ? substr($match[0], 0, $pos) : '*';
+                $value = \substr($match[0], $pos+1);
+
+                if (\trim($value, ', ') == 'first-child') {
+                    $value = 'nth-child(1)';
+                }
+                else if (\trim($value, ', ') == 'last-child') {
+                    $value = 'nth-last-child(1)';
+                }
+                else if (\trim($value, ', ') == 'first-of-type') {
+                    $value = 'nth-of-type(1)';
+                }
+                else if (\trim($value, ', ') == 'last-of-type') {
+                    $value = 'nth-last-of-type(1)';
+                }
+
+                if (preg_match("/^(nth-child|nth-of-type)\(\d+\)$/", \trim($value, ', '))) {
+                    preg_match_all("/^(nth-child|nth-of-type)\((\d+)\)$/", \trim($value, ', '), $matches, PREG_SET_ORDER);
+                    $key = (int) $matches[0][2];
+                } else if (preg_match("/^(nth-last-child|nth-last-of-type)\(\d+\)$/", \trim($value, ', '))) {
+                    preg_match_all("/^(nth-last-child|nth-last-of-type)\((\d+)\)$/", \trim($value, ', '), $matches, PREG_SET_ORDER);
+                    $key = - (int) $matches[0][2];
+                }
+                $isNthOfType = preg_match("/^nth(-last)?-of-type\(\d+\)$/", \trim($value, ', '));
+            }
+
             // and final attribute selector
-            if (!empty($match[4])) {
+            else if (!empty($match[4])) {
                 $key = \strtolower($match[4]);
             }
-            if (!empty($match[5])) {
+            else if (!empty($match[5])) {
                 $operator = $match[5];
             }
             if (!empty($match[6])) {
@@ -98,7 +129,8 @@ public function parseSelectorString(string $selector): ParsedSelectorCollectionD
                 $key,
                 $value,
                 $noKey,
-                $alterNext
+                $alterNext,
+                $isNthOfType
             );
             if (isset($match[7]) && \is_string($match[7]) && \trim($match[7]) == ',') {
                 $selectors[] = ParsedSelectorDTO::makeFromRules($rules);
diff --git a/src/PHPHtmlParser/Selector/Seeker.php b/src/PHPHtmlParser/Selector/Seeker.php
index abd6dc4e..3be94cc0 100644
--- a/src/PHPHtmlParser/Selector/Seeker.php
+++ b/src/PHPHtmlParser/Selector/Seeker.php
@@ -6,6 +6,7 @@
 
 use PHPHtmlParser\Contracts\Selector\SeekerInterface;
 use PHPHtmlParser\Dom\Node\AbstractNode;
+use PHPHtmlParser\Dom\Node\HtmlNode;
 use PHPHtmlParser\Dom\Node\InnerNode;
 use PHPHtmlParser\Dom\Node\LeafNode;
 use PHPHtmlParser\DTO\Selector\RuleDTO;
@@ -19,27 +20,25 @@ class Seeker implements SeekerInterface
      *
      * @var InnerNode[]
      *
-     * @throws ChildNotFoundException
+     * @Return AbstractNode[]
      */
     public function seek(array $nodes, RuleDTO $rule, array $options): array
     {
-        // XPath index
-        if ($rule->getTag() !== null && \is_numeric($rule->getKey())) {
-            $count = 0;
+
+        if ($rule->getTag() == '+' || $rule->getTag() == '~') {
+            $result = [];
             foreach ($nodes as $node) {
-                if ($rule->getTag() == '*'
-                    || $rule->getTag() == $node->getTag()
-                        ->name()
-                ) {
-                    ++$count;
-                    if ($count == $rule->getKey()) {
-                        // found the node we wanted
-                        return [$node];
+                if ($rule->getTag() == '+') {
+                    $result[] = $node->nextSibling();
+                } else {
+                    while ($node->hasNextSibling()) {
+                        $result[] = $node->nextSibling();
+                        $node = $node->nextSibling();
                     }
                 }
             }
 
-            return [];
+            return $result;
         }
 
         $options = $this->flattenOptions($options);
@@ -62,16 +61,34 @@ public function seek(array $nodes, RuleDTO $rule, array $options): array
                     continue;
                 }
 
-                $pass = $this->checkTag($rule, $child);
-                if ($pass && $rule->getKey() !== null) {
-                    $pass = $this->checkKey($rule, $child);
+                if (!$child instanceof HtmlNode) {
+                    $child = $this->getNextChild($node, $child);
+                    continue;
                 }
-                if ($pass &&
-                    $rule->getKey() !== null &&
-                    $rule->getValue() !== null &&
-                    $rule->getValue() != '*'
-                ) {
-                    $pass = $this->checkComparison($rule, $child);
+
+                $pass = true;
+
+                if ($rule->getTag() !== null && \is_numeric($rule->getKey()) && $node instanceof HtmlNode) {
+                    $children = $rule->isNthOfType() ?
+                        $node->childElementsOfType($child->getTag()->name()) :
+                        $node->childElements();
+                    $n = $rule->getKey() < 0 ? count($children) + $rule->getKey() : $rule->getKey()-1;
+                    $pass = $n >= 0 && $n < count($children) && $child == $children[$n];
+                }
+
+                if ($pass) {
+                    $pass = $this->checkTag($rule, $child);
+                    if ($pass && $rule->getKey() !== null && !\is_numeric($rule->getKey())) {
+                        $pass = $this->checkKey($rule, $child);
+                    }
+                    if ($pass &&
+                        $rule->getKey() !== null &&
+                        $rule->getValue() !== null &&
+                        $rule->getValue() != '*' &&
+                        !\is_numeric($rule->getKey())
+                    ) {
+                        $pass = $this->checkComparison($rule, $child);
+                    }
                 }
 
                 if ($pass) {
diff --git a/src/PHPHtmlParser/Selector/Selector.php b/src/PHPHtmlParser/Selector/Selector.php
index 697fb9cd..12150e8b 100755
--- a/src/PHPHtmlParser/Selector/Selector.php
+++ b/src/PHPHtmlParser/Selector/Selector.php
@@ -70,14 +70,19 @@ public function find(AbstractNode $node): Collection
             }
 
             $options = [];
+            $lastRule = null;
             foreach ($selector->getRules() as $rule) {
-                if ($rule->isAlterNext()) {
+                if ($rule->getTag() == '*' && $lastRule && ($lastRule->getTag() == '+' || $lastRule->getTag() == '~')) {
+                    continue;
+                }
+                if ($rule->isAlterNext() && $rule->getTag() == '>') {
                     $options[] = $this->alterNext($rule);
                     continue;
                 }
                 $nodes = $this->seeker->seek($nodes, $rule, $options);
                 // clear the options
                 $options = [];
+                $lastRule = $rule;
             }
 
             // this is the final set of nodes
diff --git a/tests/Selector/SeekerTest.php b/tests/Selector/SeekerTest.php
index d9e0e824..e4263bb0 100644
--- a/tests/Selector/SeekerTest.php
+++ b/tests/Selector/SeekerTest.php
@@ -2,6 +2,7 @@
 
 declare(strict_types=1);
 
+use PHPHtmlParser\Dom\Node\HtmlNode;
 use PHPHtmlParser\DTO\Selector\RuleDTO;
 use PHPHtmlParser\Selector\Seeker;
 use PHPUnit\Framework\TestCase;
@@ -22,4 +23,178 @@ public function testSeekReturnEmptyArray()
         $results = $seeker->seek([], $ruleDTO, []);
         $this->assertCount(0, $results);
     }
+
+    public function testSeekNthChild()
+    {
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            '*',
+            '=',
+            1,
+            null,
+            false,
+            false
+        );
+
+        $test = new HtmlNode('div');
+        $p1 = new HtmlNode('p');
+        $div = new HtmlNode('div');
+        $p2 = new HtmlNode('p');
+        $test->addChild($p1);
+        $test->addChild($div);
+        $test->addChild($p2);
+
+        $seeker = new Seeker();
+
+        $results = $seeker->seek([$test], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('p', $results[0]->getTag()->name());
+
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            '*',
+            '=',
+            -1,
+            null,
+            false,
+            false
+        );
+
+        $results = $seeker->seek([$test], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('p', $results[0]->getTag()->name());
+    }
+
+    public function testSeekNthOfType()
+    {
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            'div',
+            '=',
+            1,
+            null,
+            false,
+            false,
+            true
+        );
+
+        $test = new HtmlNode('div');
+        $p1 = new HtmlNode('p');
+        $div = new HtmlNode('div');
+        $p2 = new HtmlNode('p');
+        $test->addChild($p1);
+        $test->addChild($div);
+        $test->addChild($p2);
+
+        $seeker = new Seeker();
+
+        $results = $seeker->seek([$test], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('div', $results[0]->getTag()->name());
+
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            'p',
+            '=',
+            2,
+            null,
+            false,
+            false,
+            true
+        );
+
+        $results = $seeker->seek([$test], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('p', $results[0]->getTag()->name());
+        $this->assertTrue($results[0] === $test->lastChild());
+
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            'p',
+            '=',
+            -1,
+            null,
+            false,
+            false,
+            true
+        );
+
+        $results = $seeker->seek([$test], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('p', $results[0]->getTag()->name());
+        $this->assertTrue($results[0] === $test->lastChild());
+    }
+
+    public function testSeekNextOne()
+    {
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            '+',
+            '=',
+            null,
+            null,
+            false,
+            false
+        );
+
+        $test = new HtmlNode('div');
+        $p1 = new HtmlNode('p');
+        $div = new HtmlNode('div');
+        $p2 = new HtmlNode('p');
+        $test->addChild($p1);
+        $test->addChild($div);
+        $test->addChild($p2);
+
+        $seeker = new Seeker();
+
+        $results = $seeker->seek([$p1], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('div', $results[0]->getTag()->name());
+
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            '+',
+            '=',
+            null,
+            null,
+            false,
+            false
+        );
+
+        $results = $seeker->seek([$div], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('p', $results[0]->getTag()->name());
+    }
+
+    public function testSeekNextAll()
+    {
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            '~',
+            '=',
+            null,
+            null,
+            false,
+            false
+        );
+
+        $test = new HtmlNode('div');
+        $p1 = new HtmlNode('p');
+        $div = new HtmlNode('div');
+        $p2 = new HtmlNode('p');
+        $test->addChild($p1);
+        $test->addChild($div);
+        $test->addChild($p2);
+
+        $seeker = new Seeker();
+
+        $results = $seeker->seek([$p1], $ruleDTO, []);
+        $this->assertCount(2, $results);
+        $this->assertEquals('p', $results[1]->getTag()->name());
+
+        $ruleDTO = RuleDTO::makeFromPrimitives(
+            '~',
+            '=',
+            null,
+            null,
+            false,
+            false
+        );
+
+        $results = $seeker->seek([$div], $ruleDTO, []);
+        $this->assertCount(1, $results);
+        $this->assertEquals('p', $results[0]->getTag()->name());
+    }
 }