This paper examines divisions between majority and minority ethnic groups over attitudes towards minority rights in 13 East European societies. Using national sample surveys and multilevel models, we test the effectiveness of competing explanations of ethnic polarization in attitudes towards minority rights, as well as regional and cross-national differences in levels of polarization. We find that, at the individual level, indicators of 'social distance' (inter-marriage and social interaction) account most effectively for the extent of ethnic polarization. However, regional and cross-national variations in polarization between majority and minority groups are explained most effectively by cultural (linguistic and religious) differences. These findings accord with research in the West, indicating the importance of cultural differences as a source of ethnic polarization, while offering little support for theories focusing on economic and structural factors or the size of minority groups. They also suggest the likely sources of difficulties for democratic consolidation in ethnically divided post-communist societies.