diff --git a/apps/advanced/README.md b/apps/advanced/README.md
index f2abc1e..59a1b77 100644
--- a/apps/advanced/README.md
+++ b/apps/advanced/README.md
@@ -54,6 +54,7 @@ REQUIREMENTS
 
 The minimum requirement by Yii is that your Web server supports PHP 5.3.?.
 
+In order for captcha to work you need either GD2 extension or ImageMagick PHP extension.
 
 INSTALLATION
 ------------
diff --git a/apps/basic/README.md b/apps/basic/README.md
index 2f8f1e8..31b5ecc 100644
--- a/apps/basic/README.md
+++ b/apps/basic/README.md
@@ -33,6 +33,7 @@ REQUIREMENTS
 
 The minimum requirement by Yii is that your Web server supports PHP 5.3.?.
 
+In order for captcha to work you need either GD2 extension or ImageMagick PHP extension.
 
 INSTALLATION
 ------------