I finally found the solution (or let's say wcasatti from Exadel forum told me how to do it right): With the a4j:region tag you can define which components shall be decoded during the JSF lifecycle. This is where the language barrier was a problem for me since didn't understand that "decode" meant "process" (but I think some native speakers didn't catch that either *g*). So if define a a4j:region around the select menu 1 then only this single component is validated. That's what I wanted. But in order to create the output for the new menu 2 I need to set the attribute renderRegionOnly to "false", so that the other components are included in the AJAX response, too. Well, here's the code: | <a4j:region renderRegionOnly="false"> | <h:selectOneMenu id="menu1" value="..." required="true"> | <f:selectItems ... /> | <a4j:support event="onchange" reRender="menu2" /> | </h:selectOneMenu> | </a4j:region> | | <h:selectOneMenu id="menu2" .... | .... PS: I think that the attribute ajaxSingle should be deprecated. It might leads to problems and a4j:region does it much better :). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3972227#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...