The work describes the anatomical structure of the cerebellum of the caspian seal (Pusa caspica Gmelin) and Greenland seal (Pagophoca groenlandica Erxleben). The shape of the cerebellum, the disposition of the main lobes and convolutions are characterized. The schemes of three projections of the cerebellum of both species are presented. The figures of the cerebellum size, its absolute and relative weight and the surface of the cerebellum and its portions in seals have been obtained. The well-developmed flocculo-nodular portions and paraflocculuses and relatively poorly developed lobulus paramedianus are pointed to be one of the characteristic features of the structure of the seal cerebellum. An attempt is made to explain great dimensions of the flocculo-nodullar portion and paraflocculuses by specific features of the seal locomotion in water.