The changes in the area of the lake on the territory of thermokarst-lake plains were studied using multi-temporal satellite images Landsat, obtained over a period of four decades. Chosen 53 test sites were located in the subzone of continuous permafrost in Western and Eastern Siberia and in different landscape zones of studied territory. From a few hundred to a few thousand thermokarst lakes were identified at each test site. Lake areas were measured by means of satellite images of geographic information system ArcGIS 9.3. It is shown that in Western Siberia on average there is a tendency of reducing the total area of the lakes. But there is the specific feature of the latitude dependence of the dynamics of the lake areas: at latitudes greater than 70° N. dominated by the growth of the total area of lakes and at latitudes less than 70° N. there is a tendency to reduce their areas. On the territory of Eastern Siberia permafrost prevails on average increase in the area of thermokarst lakes. Unlike Eastern Siberia in the subzone of continuous permafrost in Western Siberia near the values of 70° N. is found the transition zone from the trend of reducing the lake areas to trend of their growth with increasing latitude.