[en] Sedimentation rates at 98 stations in several coastal and open sea areas in the Gulf of Finland were determined using ¹³⁷Cs distribution in sediment profiles. The ¹³⁷Cs activities of the sediment cores were measured using direct gamma spectrometric measurements either on board research vessels or at the respective institutes. Relative rates were calculated. The highest activities are found in layers corresponding to the year 1986 from areas mostly affected by the fallout cloud of the Chernobyl nuclear power plant accident. The areal distribution of ¹³⁷Cs in sediments is correlated with that measured on land but the activities and distribution pattern in sea sediments has been modified by drainage from land and secondary transport in the sea