diff --git a/models/Table/CollectionTree.php b/models/Table/CollectionTree.php
index f52624f..e7ec0db 100644
--- a/models/Table/CollectionTree.php
+++ b/models/Table/CollectionTree.php
@@ -21,6 +21,14 @@ class Table_CollectionTree extends Omeka_Db_Table
      */
     protected $_collections;
 
+    /**
+     * Cache of children of a collection.
+     *
+     * It's an associative array where keys are collection ids and values are
+     * arrays of children ids.
+     */
+    protected $_collectionsChildren;
+
     /**
      * Cache of variables needed for some use.
      *
@@ -271,12 +279,14 @@ public function getCollection($collectionId)
     public function getChildCollections($collectionId)
     {
         $childCollections = array();
-        $collections = $this->_getCollections();
-        foreach ($collections as $collection) {
-            if ($collectionId == $collection['parent_collection_id']) {
-                $childCollections[$collection['id']] = $collection;
+        $collectionsChildren = $this->_getCollectionsChildren();
+
+        if (isset($collectionsChildren[$collectionId])) {
+            foreach ($collectionsChildren[$collectionId] as $childId) {
+                $childCollections[$childId] = $this->getCollection($childId);
             }
         }
+
         return $childCollections;
     }
 
@@ -365,6 +375,26 @@ protected function _getCollections()
         return $this->_collections;
     }
 
+    /**
+     * Cache collections children data in an associative array.
+     */
+    protected function _getCollectionsChildren()
+    {
+        if (is_null($this->_collectionsChildren)) {
+            $collections = $this->_getCollections();
+
+            $this->_collectionsChildren = array();
+            foreach ($collections as $id => $collection) {
+                if ($collection['parent_collection_id']) {
+                    $parent_collection_id = $collection['parent_collection_id'];
+                    $this->_collectionsChildren[$parent_collection_id][] = $id;
+                }
+            }
+        }
+
+        return $this->_collectionsChildren;
+    }
+
     /**
      * Reset the cache property.
      */