Major and largest cities are now becoming the dominant form of settlement of the population. Their internal economic, social, and demographic differences are subject to interdisciplinary research. This paper discusses the spatial variability of social and demographic indicators for municipalities of St. Petersburg. The analysis of territorial differences in the composition of the population give a chance us to identify types of urban areas with a certain age and educational structure. This makes it possible to further focus on identifying the causes of the socio-demographic segmentation of the urban space of St. Petersburg.