ENThe paper deals with the problems of ethnic diversity of the regions (NUTS 3) belonging to Poland, Lithuania and Latvia, situated along the eastern borderland of the European Union. The ethnic factor, namely, influences in an important manner the shape of public life in all three regions. It impacts, as well, on mutual relations between the three countries, and on the relations between them, on the one hand, and their eastern neighbours, not being the members of the European Union, on the other (Belarus’, Russian Federation). The complex ethnic landscape may turn out to be a negative, as well as positive factor of the regional development. Key words: Poland, Lithuania, Latvia, EU Eastern Borderland regions, ethnic diversity.