Numerous researchers have claimed that individuals begin to conceptualize their own thoughts and of others upon attainment of formal operational thought at adolescence. This claim suggests that events within the course of cognitive development may also contribute to the onset and resolution of adolescent identity formation. Various attempts have been made to explore the relations between cognitive development and Ego Identity (EI). Most research was related to Marcia’s four identity statuses. The research findings so far portray an ambiguous picture about the relation between EI and cognitive ability. In this paper we will focus on two cognitive aspects: cognitive ability and cognitive modifiability in relation to EI development.