During the last few decades, ideas about household structures in the territories lying east of the Hajnal line have changed considerably. Not only has the line itself been transformed into a fairly wide ‘transitional’ zone and its location on the European map been changed, but the variety of family forms found behind the generalised characteristics of the “Eastern” territories has made scholars re-examine certain theoretical concepts and findings. The new concepts are based on the growing number of micro-studies covering the territories of Central and Eastern Europe and provide very detailed information on family size and structures. For Russia, which has always been considered a model of the Eastern type of household organisation, new data have appeared as well, making it possible to re-examine the theories concerning Russian households. However, scholars more often pay attention to geographic rather than social stratification of household types. The majority of studies are devoted to the social group of peasants, especially of peasant serfs, while household structures in other social groups are less explored. In this article, we seek to fill this gap by providing a comparison of household structures in two social groups, namely of Moscow merchants and of serfs who lived near Moscow in the middle of the 19th century. The household structures in the two groups were entirely different: one in two merchant families was a nuclear one consisting of a couple with or without children, or a single parent with children, while in the peasant population multiple households, including several nuclear families, predominated (60% of the total number of households). The most likely explanation for this is the two groups’ different obligations to the state.