diff --git a/component/Geography/Fr/CodePostal.php b/component/Geography/Fr/CodePostal.php
index 9aac721..f096ca3 100755
--- a/component/Geography/Fr/CodePostal.php
+++ b/component/Geography/Fr/CodePostal.php
@@ -17,4 +17,20 @@ public function __construct(string $code)
 
         parent::__construct($code);
     }
+
+    public function getNumeroDepartement(): NumeroDepartement
+    {
+        $numeroDepartement = substr($this->value, 0, 2);
+        $numeroDepartement = match($numeroDepartement) {
+            '20' => match (substr($this->value, 0, 3)) {
+                '201' => '2A',
+                '202' => '2B',
+            },
+            '97' => substr($this->value, 0, 3),
+            '98' => substr($this->value, 0, 3),
+            default => $numeroDepartement,
+        };
+
+        return new NumeroDepartement($numeroDepartement);
+    }
 }
diff --git a/test/Geography/Fr/CodeCommuneTest.php b/test/Geography/Fr/CodeCommuneTest.php
index 75a70fa..df002e9 100644
--- a/test/Geography/Fr/CodeCommuneTest.php
+++ b/test/Geography/Fr/CodeCommuneTest.php
@@ -18,9 +18,6 @@ public function testInterface(): void
 
         $this->assertIsString($codeCommune->value);
         $this->assertEquals('97421', $codeCommune->value);
-
-        $this->assertIsObject($codeCommune->getNumeroDepartement());
-        $this->assertEquals('974', (string)$codeCommune->getNumeroDepartement());
     }
 
     public function testNotCompliant(): void
@@ -29,4 +26,15 @@ public function testNotCompliant(): void
 
         new CodeCommune('690I');
     }
+
+    public function testGetNumeroDepartement(): void
+    {
+        $codeCommune = new CodeCommune('69001');
+        $this->assertIsObject($codeCommune->getNumeroDepartement());
+        $this->assertEquals('69', (string)$codeCommune->getNumeroDepartement());
+
+        $codeCommune = new CodeCommune('97421');
+        $this->assertIsObject($codeCommune->getNumeroDepartement());
+        $this->assertEquals('974', (string)$codeCommune->getNumeroDepartement());
+    }
 }
diff --git a/test/Geography/Fr/CodePostalTest.php b/test/Geography/Fr/CodePostalTest.php
index f29dff9..469daab 100644
--- a/test/Geography/Fr/CodePostalTest.php
+++ b/test/Geography/Fr/CodePostalTest.php
@@ -26,4 +26,27 @@ public function testNotCompliant(): void
 
         new CodePostal('690I');
     }
+
+    public function testGetNumeroDepartement(): void
+    {
+        $codePostal = new CodePostal('69001');
+        $this->assertIsObject($codePostal->getNumeroDepartement());
+        $this->assertEquals('69', (string)$codePostal->getNumeroDepartement());
+
+        $codePostal = new CodePostal('20169');
+        $this->assertIsObject($codePostal->getNumeroDepartement());
+        $this->assertEquals('2A', (string)$codePostal->getNumeroDepartement());
+
+        $codePostal = new CodePostal('20290');
+        $this->assertIsObject($codePostal->getNumeroDepartement());
+        $this->assertEquals('2B', (string)$codePostal->getNumeroDepartement());
+
+        $codePostal = new CodePostal('97400');
+        $this->assertIsObject($codePostal->getNumeroDepartement());
+        $this->assertEquals('974', (string)$codePostal->getNumeroDepartement());
+
+        $codePostal = new CodePostal('98735');
+        $this->assertIsObject($codePostal->getNumeroDepartement());
+        $this->assertEquals('987', (string)$codePostal->getNumeroDepartement());
+    }
 }