The leachability of radiocaesium in a land-sea system was tested in laboratory experiments. The leaching test was carried out utilising sediment from the cliff at Ustka, melting snow and sea-water. No desorption of radiocaesium was detected for sediment loads of 3,8 and 16,5 g?dm-3. Leaching reactions of radiocaesium under field were investigated in a comparison of radioactivity in sandy beach samples continuously (water line) and occasionally (middle of the beach) washed by the sea and in samples with little or no contact with seawater (dune footstep or dune cliff). Radiocaesium deposition in sandy sediments water-line and mid-beach were found to be the same. The activity of this radionuclide in sandy beach samples collected at Krynica Morska, Sopot, Hel and Ustka was compared to that in marine sediments and soils of northern Poland. In addi-tion, the depth of radiocaesium penetration into sediments in the Polish littoral zone was estab-lished.