The results of a syntaxonomical study of plant communities of the large lake Donty (North-East of the European part of Russia) are presented. The diversity of hydrophytic vegetation has been classified into 3 classes (Lemnetea, Potametea and Phragmito-Magnocaricetea), 5 orders, 8 alliances, 20 associations and 1 community. Subassociation Scolochloetum festucaceae caricetosum aquatilis is new. Communities of associations Caricetum aquatilis, Equisetetum fluviatilis, Potamo—Nupharetum luteae, Potametum perfoliati are mostly wide distributed, while these of Phragmitetum communis, Scolochloetum festucaceae ones are relatively rare as well as Lemno—Spirodeletum polyrchizae, Elodeo—Potametum alpini, Potamo—Nupharetum pumilae, Potametum praelongi and Scirpetum lacustris are very rare. Some communities contain 2 regional rare species: Scolochloa festucacea and Ranunculus lingua.