The forest is about 2/3 territory of the Ukraine, contaminated after Chernobyl accident. It has accumulated 3.2*E15 Bq radionuclides of cesium and strontium. Twenty observationsites were established in the forests on Northern, Western and Southern directions from Chernobyl NPP. During three years the samples of soil, litter, plants, trees, animals have collected and activity measured. Also the depth distribution of activity in the soil and mobility of the radionuclides have measured. It was found the main part of radionuclides is still in the top layer of the soil and litter. Strontium has higher mobility than cesium and its depth distribution is less slopping. Litter has role of a secondary source of radioactivity and continuously contaminated the plants and mushrooms.