In ethnic studies, a multidimensional concept of social integration deals with the analysis of differentiation of actions and relations among ethnic groups, quantitative and qualitative aspects of ethnic structure. The article covers main theoretical assumptions and definition of main empirical dimensions, which are based on the overview of empirical studies. The theoretical and empirical scheme of sociologist A.Diaz is presented in more detail. Also, the author elaborates on the relevancy of the concept of social integration with regard to the ethnic structure of Lithuania. Social integration is conceived through ethnic groups’ social resources (e.g., social networks, command of language, education, social standing, etc.) and the available formal possibilities (political, legal measures) within a specific society, the lack of which contributes to social exclusion or marginalisation. The understanding of ethnic minority groups’ participation in society is widened through the discussion of the following factors of social integration: social resources, inclusion to social relation networks, participation in different employment sectors and other institutional formations, social position, and positive attitudes of majority and minority groups. The author concludes that insufficient participation of ethnic groups in different levels of social spheres or concentration at certain levels may contribute to the formation of ethnic cleavages
