In greenhouses of botanical gardens of Ukraine 81 species of nematodes were found. The richest by the number of species was Tylenchida order that was presented by 25 species (31 % of species composition). The dominant group of nematodes was plant-parasitic (most frequent was Rotylenchus robustus (de Man, 1876) Filipjev, 1936 and Meloidogyne incognita (Kofoid et White, 1919) Chitwood, 1949). The group of saprobiotic nematodes, which was presented by 52 species (64 %), appeared to be the richest by the number of species. It is shown, that formation of nematode communities in greenhouses of botanical gardens was caused by the interaction of many related factors, crucial of which is the composition of plant collections. The structure of communities is quite constant and almost independent of the quantity of nematodes species. Plant-parasitic species dominate by the number and frequency of detection, and represent a kind of a core of nematode communities.