Аннотация:This paper presents an assessment of the modern radioecological situation in forest (pine, spruce,and birch forests) and fallow ecosystems in contaminated areas of Kaluga oblast, Russian Federation. The densities of soil contamination with natural radionuclides ( 226 Ra, 232 Th, and 40 K) in the study area conform to the background levels; while the soil contamination with the technogenic radionuclide ( 137 Cs) significantly exceeds the background level (3 kBq/m 2 ) varying from 60.8 to 273.8 kBq/m 2 . Forest ecosystems (especially coniferous ones) are contaminated with 137 Cs to the highest extent, while fallow ecosystems are least contaminated. The 137 Cs contamination density in the soils has decreased by more than 3 times in comparison with the initial period after the fallout (1986); however, it still significantly exceeds the permissible level 37 kBq/m 2 ). The total specific activity of soils and equivalent absorbed dose rates in ecosystems of contaminated areas are primarily determined by the 137 Cs contribution; while, in background areas, it is determined by the 40 K contribution.