The present studies revealed different factors associated with the reported advantages found in fully bilingual children for metalinguistic awareness and executive control. Participants were 100 children in Study 1 and 80 children in Study 2 in the process of becoming bilingual by attending immersion programs. In both studies, "level of proficiency" in the language of testing was related to performance on metalinguistic tasks and "length of time" in the immersion program was related to performance on executive control tasks. This dissociation is consistent with models of lifespan development that distinguish between representational structure and executive control. (Contains 6 tables and 1 figure.)