In this paper we report the preliminary results of a study of palaeogeography of the Lake S one geosystem, which is situated in the Che m Hills region. Due to very small lake surface (3.4 ha) and large area of lake catchment (526.4 ha) the Lake S one geosystem is an excellent object of palaeogeographical studies. The detailed geological examination of the lake geosystem allowed us to reconstruct the shape of sedimentation palaeobasin as well as vertical and horizontal lithofacial variability of deposits. Based on the initial results of pollen analysis, we distinguished eight local pollen assemblage zones, which were related to the Late Glacial and Holocene periods. In this stage of palynological investigations the boundaries of pollen zones and the Late Glacial and Holocene phases were determined only approximately. The analysis of Ostracoda fauna established the occurrence of 18 species. Based on species composition, we distinguished 16 phases of Ostracoda development corresponding to the periods in which species composition was different or the abundance of individual species considerably changed. The obtained results of sedimentological, pollen and fossil Ostracoda analyses allowed us to determine the main stages of evolution of the S one lake-mire geosystem. Main directions of the recorded changes are similar in all cases. The differences that appeared on the attempts to determine precisely the boundaries between successive phases will be explained in the further research on the Lake S one geosystem.