Brief characteristics, original pictures, ecology and distribution of the three Nostoc species (N. carneum, N. ellipsosporum, and N. spongiaeforme) new in Lithuania are provided. Several morphological features of specimens found in Lithuania do not correspond to the typical description of species: N. carneum heterocytes are elliptical and spherical, vegetative cells are with aerotops; N. ellipsosporum akinetes are cylindrical, elliptical and spherical; N. spongiaeforme heterocytes are located single or in rows; akinetes are oblong and elliptical. New data on earlier described Nostoc species (N. caeruleum, N. commune, N. linckia, N. pruniforme, N. punctiforme, N. verrucosum) in Lithuania are also provided.
Keywords: new species, Nostoc, freshwaters, Lithuania.