Digital mapand attributive databases on the forest fund of two clusters (Kostomuksky Strict Nature Reserve and Kalevalsky National Park) now comprised within the joint federal protected area Kostomukshsky SNR have been analysed. Forest ecosystems of the strict nature reserve and the national park were found to be typical of the northern taiga subzone in terms of species composition, forest type structure and productivity levels. The two areas had a similar distribution of relatively even-aged, uneven-aged and all-aged pine stands, the ratio being around 5:4:1. Kalevalsky NP forests are described as older, less productive and less disturbed by humans compared to forests of Kostomukshsky reserve. A distinctive feature of the national park is the extensive (several thousands of hectares in area) forest tracts of relatively even-aged pine and spruce stands. Their history of origin is still a question. As for the strict nature reserve, the spatial structure of its forests is noted for concentrated growth of relatively even-aged pine stands younger than VII age class in the environs of Lake Kamennoye. This enables quite accurately delineating the zone of active land use in the area during the past 100-150 years.