As per the EJB3 Persistence spec section 6.2.2, the persistence unit if packaged in a ejb .jar is visible only within that jar (unless you use the jarname#unitname convention while injecting the persistence context). However if you package the persistence.xml in the META-INF folder of the .ear then it will be visible to all components in the ear. Having said that i don't know why the presence/absence of EJBs in the persistence jar should show a different behaviour (probably the deployment order of the component changes when the EJBs are added?). View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4256084#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...