This paper analyses the interrelationship between the process of suburbanization and a changing political and ethnic landscape in the Vilnius urban region. The region surrounding Vilnius city is dominated by Polish identity residents while those who suburbanise into the region are mainly ethnic Lithuanians. This may lead to potential tension and conflicts in the region which may find its expression in the voting behaviour of residents of the region. Using data from the 1997 and 2011 municipal elections we found that the share of votes for the Polish party in the region decreases over time, while the absolute number of votes for this party increases. At the same time we find increasing voting activity in the suburban ring. The changing electoral behaviour can be regarded as an indicator of a growing ethnic identity. The voting results also identify the zones of the most intense changes in the electoral behavior and thus indicate areas of potential social tensions between two ethnic groups.