Аннотация:The article is a continuation of a series of publications devoted to the analysis of the industry specialization of Russian monotowns. The purpose of the paper is to analyze the sectoral structure of the industry of a monotown and assess its importance for the economic development of a monotown. The object of the paper is the sectoral structure of a monotown. The paper examines the sectoral specialization of the industry of two constituent entities of the Northwestern Federal District (NWFD), namely the Arkhangelsk and Vologda regions, and also analyzes the monotowns located in these regions. As a result of the research, the authors come to the conclusion that the sectoral specialization of the Northwestern Federal District is heterogeneous and the main branches of specialization are manufacturing, mining, and trade. It is concluded that the level of socio-economic development of a single-industry town does not depend on the sectoral specialization of the town-forming enterprise. The problems common to the monotowns considered in the paper are highlighted: low living standards of the population and its outflow, lack of qualified personnel, as well as insufficient attention from the state and business. The results of the study can be used to develop measures to diversify the economy of single-industry towns, strategize their development, form state and regional policies in the field of modernization of single-industry towns.