The diversity and distribution of Cyanoprokaryota/Cyanophyta was studied in freshwater and terrestrial ecosystems of the typical arctic and sub-arctic tundra of East-European Russia. Samples were taken in the Bolshezemelskaya and the Malozemelskaya tundras and in some arctic islands. It is shown that Cyanoprokaryota are one of key groups in the taxonomic structure of algae flora in studied regions. Distribution of cyanophytes is registered in various plant communities of freshwater and terrestrial tundra ecosystems. In the ecosystems of the East-European tundra 334 species were identified. 304 species in water bodies and 158 in soils were found. They belong to 4 divisions, 20 families and 69 genera (more than 14% of the total diversity of algae in this region). The Nostocaceae, Phormidiaceae, and Oscillatoriaceae families are characterized by the highest species diversity. 31% of the total Cyanoprokaryota group is heterocytic algae which are potentially able to fix nitrogen.