The results of studying the changes in thermocarst lakes of Russia based on comparing space images from Landsat satellites taken at an interval of approximately 20 years are presented. Comparison of multi-temporal images was made for 13 test sites in various areas of the cryolithozone (north of the European part of Russia, Western Siberia, north of Eastern Siberia, Transbaikal hollows, Central Yakutia, the Far East and Chukotka). In total, a little more than 117,000 lakes are covered by the study. Interpretation of space images is performed with QGIS software complex in automated mode using spectral index NDWI. The analysis of data at most reference sites (9 of 13) revealed negative dynamics both in the area and the number of lakes. The largest changes were recorded for ponds (area up to 5 hectares) – a reduction in the number and area by 12%. Minimal losses were identifi ed for the “very large lakes” group – 6.2 and 3 %, respectively. The increase in average annual air temperatures observed in most reference areas did not cause a widespread increase in the number and total area of thermocarst lakes. Only in 3 sections (Yessei and Verkhneangarsk hollows, Lena river delta), the increase in lake areas was most likely the result of the activation of thermocarst and thermoabrasion processes under conditions of rising average annual air temperature. It was concluded that the connection between the dynamics of lakes and the nature of permafrost rocks is not traced: for both continuous and island distribution, multi-directional changes in the number and area of lakes are characteristic.