We investigated changes in the size of thermokarst lakes on the territory of the continuous permafrost zone of Siberia by using Landsat multi-temporal cloudless space images of moderate spatial resolution as obtained during 1971–2013. The study was carried out in 57 test areas belonging to different landscape zones of the territory of the continuous permafrost zone in Western and Eastern Siberia. The selected areas were of about the same size (with the area averaging 3.5 thou km2). Analysis of the landscape characteristics of the study territory revealed new regularities. It is established that the territory of the continuous permafrost zone of Western Siberia is dominated by a tendency for a decrease in the areas for the period of investigations. The continuous permafrost zone of Eastern Siberia shows a tendency for an increase in the total lake area, whereas the subarctic zone, in both Western and Eastern Siberia, shows a tendency for a decrease in the lake area. It is found that a decrease in the lake area in the subarctic zone is more pronounced in Western Siberia where the relative value of change in the total lake area reaches nearly 6 %, on the average (as contrasted to 0.5 % in the subarctic zone of Eastern Siberia). It is shown that a predominance of the tendency for an increase in the lake area might well be the most characteristic feature of the dynamics of the thermokarst lake areas in the forest-tundra and taiga zones of Eastern Siberia.Keywords: permafrost, thermokarst lakes, global warming, multi-temporal space images, landscape analysis, Siberia.