The article summarizes data on diversity, cenotic features, ecology and distribution of aquatic vegetation of the Lemnetea class in the south-east of West Siberia. 143 complete geobotanical relevés performed in 1995–2017 in Novosibirsk and Kemerovo regions, Altai Territory and Altai Republic were used. The cenotic diversity of the Lemnetea class identified was 11 associations of 3 unions and 1 order of the Braun-Blanquet approach, which is slightly higher than that identified for East Siberia (8 synthaxa of the association rank). Ceratophylletum demersi, Lemno-Utricularietum vulgaris and Stratiotetum aloidis were found in all natural zones – the forest belt of the Altai-Sayan mountain system, the forest-steppe and steppe zones. Lemno-minoris–Spirodeletum polyrhizae and Lemno-minoris–Riccietum fluitantis were noted only in the fresh waters of the Altai-Sayan mountain system and the Ob region. Salvinio natantis–Spirodeletum polyrhizae, and Utricularietum macrorhizae were found only in the forest-steppe of the Ob region. Communities of Potamogetono-Ceratophylletum submersi association were noted in the forest-steppe and steppe of the plain part of the area surveyed, which is due to the presence of brackish water bodies there.Key words: syntaxonomy, aquatic vegetation, ecology, West Siberia.