The study was carried out from the beginning of June to the end of July 2005 in the Krasiborska Kępa reserve (UTM VV56; 53.848°N, 14.370°E). Three research plots were established, representing various types of use of reedy areas: an unused reedy area, a reedy area mown in summer, and an area mown in winter. Beetles were collected in Barber traps with ethylene glycol as a preservative liquid. Seven traps were set up in each examined habitat. In total 1,145 specimens belonging to 35 species were caught. The relatively small area presented three different carabid assemblages, differing in species richness, abundance, dominance structure and ecological preferences. The highest species richness and abundance, as well as the largest representation of endangered stenobiontic hygrophilous bog species (Trechus rivularis, Carabus clathratus, Carabus menetriesi, Bembidion fumigatum, Blethisa multipunctata, and Oodes helopioides), were observed in the periodically flooded fen which was mowed in the winter.