The identity development takes place during the process of integrating the past to the presence with anticipated future. Additionally, it occurs in ecological context which concerns relations and interactions at the individual, group and institutional levels, as well as changes related to the revitalization of regional cultures, the integration of states into transnational structures or the progressive processes of globalization. In the paper, the Authors mostly pay attention to ecological determinants that influence the process of identity development, which takes place in multicultural environment. The purpose of the paper is to present a new theoretical approach – Theory of Multidimensional Identity (TMI) by Jerzy Nikitorowicz. It is based on the fact that a child is located in a diverse cultural environment under the influence of traditional multiculturalism, having existed for several generations, for example, on the borderland. During different stages of identity development (from the past to the future), three groups of dimensions have been distinguished: dimensions in the context of inherited (given, taken over) identity; dimensions in the context of individually shaped and realised identity and dimensions which are socially determined. This theoretical approach allows for the analysis of dependence and relations between the different stages and dimensions of identity development. It highlights with which stages those three dimensions form the identity system, how it changes, what are the reasons for those changes and modifications.