Research into the socio-spatial dynamics in Central-Eastern European cities is an im-portant area of contemporary transition studies. Open issues in this domain range from defining a theoretical framework to data availability and methodological approaches. As to the former aspect, recent literature focuses on the hybrid nature of the post-socialist urban space, which underwent transformation in the conditions of globalization and eco-nomic liberalization; the earlier model of spatial development changed dramatically as a result. The multi-scalar and comparative approaches may shed new light on the complex patterns of urban socio-spatial differentiation and its post-Soviet dynamics. Growing regional socio-economic imbalances observed in the former socialist states are lending new urgency to this area of research. This study employs a comparative approach to investigate post-1991 socio-spatial trans-formations in St Petersburg and Riga — the two largest post-Soviet urban centres in the Baltic Sea region. An important result of the research is a methodology for multi-lev-a el analysis of changes in the urban environment of post-socialist cities. Data from post-1991 national censuses and population registers are used to calculate measures of social well-being in urban districts as well as to identify territorial imbalances. Compar-ative analysis makes it possible to trace the spatial patterns of post-Soviet differentiation and set out guidelines for further research in the area.