The impact of the moss substratum (soil or rock) on the species composition of nematode assemblages was investigated. Samples of different species of moss were collected at several stations in Italy. Nematode density was very variable between samples and substrata, but nematode assemblages were very similar in trophic group structure and diversity. Predator dominance and the high percentage of Dorylaimida indicate the good quality of the investigated stations. Species richness and biomass were higher in mosses growing on soil where large nematodes such as Aporcelaimellus obtusicaudatus were abundant. No clear substratum-dependent species pattern was found: only Tripylella intermedia appears to be exclusive for mosses growing on rocks. Prionchulus muscorum and Plectus acuminatus were the commonest species and occurred in almost all samples. By comparing our moss communities with those of other European communities reported in the literature, we detected significant differences between continental and Mediterranean communities.