Use DividedBox
<?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Panel layout="horizontal" width="100%" height="100%" title="this is a test"> <mx:DividedBox direction="vertical" width="200" height="100%"> <mx:List width="100%" height="200"> </mx:List> <mx:List width="100%"> </mx:List> </mx:DividedBox> <mx:Canvas width="100%" height="100%"> <mx:Button bottom="10" right="10" label="Save"/> </mx:Canvas> </mx:Panel> </mx:Application>