Spatial heterogeneity of the distribution of cesium-137 in the upper part of the peat soil profile of the high-bog Sodrinskoe (Mshinskoe swamp nature preserve, Leningrad region, RF) has been established. The horizontal distribution of cesium-137 is significantly influenced by the surface microrelief. Concentration of radionuclide depends on whether the sample was taken in a hollow or from a nearby bump.