The objective of the study is to investigate the effects produced by confessional belonging on the conditions of the ethnic identities of the diasporas and on the character of the inter-ethnic relations in regional communities. Religious identity can reveal itself both as a factor of inter-ethnic integration and as an additional indicator of ethnic and cultural identity that increases the distance between different groups of the population. The investigation has been developed based on the analysis of statistical and sociological data that illustrate the existence of confessionally heterogeneous ethnic diasporas in regional community. It has been established that in the Rostov region, the hub region of the South of Russia, confessional identity presents an additional factor of maintaining the ethnic identities within the ethnic and cultural communities as follows: Jews, Armenians, Greeks, Poles, Georgians, Assyrians, and Koreans. The majority of these groups possess confessional institutions of their own, though the degree of consolidation with them is different. Thus, while for Jewish and Armenian diasporas of the Don the institutions of national religion are the key forms of maintaining their identities; for Poles the importance of the confessional factor is lower, and for Greeks and Georgians this factor is purely symbolic affecting just a negligibly small part of the community. At the same time it has been established that Islamic identity of a number of diasporas that live in the territory of the Rostov region and in many other regions of the South of Russia are practically meaningless in terms of strengthening the identities of the ethnic communities, but, nevertheless it produces an effect of cultural differentiation on the system of social interactions in the environment of the regional community.