Vertigo moulinsiana is a little known, but very rare, small land snail species, living in wet areas with high pH and calcium content. The paper presents research carried out in May 2008, on one of the few sites of this species in Poland: in wetlands located in the valley of the Nida river. Based on data collected in 60 randomly selected points, it was found that Vertigo moulinsiana occurred most often and in the highest densities in places overgrown with Glyceria and sedge Carex. The occurrence of the highest density in Glyceria was under "wet" conditions. In sedge, the highest density was noted in "dry" conditions. Also affecting the differences in the population density of snails are the interactions between the type of vegetation and dampness of the conditions, which probably provide suitable microclimatic conditions for snails. Most likely, the presence of Desmoulin’s whorl snail is linked with the spatial structure of vegetation occurring under particular hydrological conditions, which allows for the development of a specific microclimate.