Use sessionScope or ApplicationScope in 10g or pageFlowScope in 11g if Dialog is used in action as shown below.
icon="../../image/result.gif"
action="dialog:GlobalRegressionComponentSummary"
actionListener="#{Back_RegressionComponentTopLevelSummary.setPageNameProp}"
useWindow="true" windowHeight="500"
windowWidth="300">
to="#{sessionScope.currentTargetLabel}"/>