At the end of summer 2021, phytocenological research was conducted on aquatic and wetland vegetation of the Pusta River - left tributary of the South Morava River. Using UPGMA classification method and the Bray-Curtis distance on a set of 97 relevés and 44 species, degree of floristic differentiation between studied vegetation plots was quantified. It was established that 7 associations take part in composing vegetation of the Pusta River – Myriophyllo-Potametum Soó 1934, Potametum nodosi Soó (1928) 1960, Segal 1964, Phragmitetum australis Savič 1926, Typhetum latifoliae Nowiński 1930, Glycerio-Sparganietum neglecti Koch 1926, Phalaridetum arundinaceae Libbert 1931 and Polygono-Bidentetum tripartitae (W. Koch 1926) Lohm. 1950. The plant associations of vegetation class Potamogetonetea Klika in Klika et Novák 1941- Potametum nodosi and Myriophyllo-Potametum, are floristically the poorest and entirely consist of native plant species. The associations of vegetation class Phragmito-Magnocaricetea Klika in Klika et Novák 1941 - Typhetum latifoliae (34 taxa), Glycerio-Sparganietum neglecti (33 taxa), Phragmitetum australis (24 taxa) and Phalaridetum arundinaceae (20 taxa) consist of higher number of species, including invasive plants. Vegetation class Bidentetea Tx. Et al. ex von Rochow 1951 is represented by only one association - Polygono-Bidentetum tripartitae, which consists of 24 taxa, with a share of 16.67% of allochthonous species. Collected phytocenological data are going to be good basis for the future research of the vegetation of lotic ecosystems in the southeastern Serbia.