The aim of this study was to determine the impact of a genetically modified (GM) maize cultivar MON 810 containing Cry1Ab protein in comparison to conventional plants on rove beetle assemblages (Coleoptera: Staphylinidae) as non-target arthropods. This is the first large-scale Bt-maize experiment in Poland. A Bt transgenic maize cultivar (DKC 3421 Yield Gard®) and the respective isogenic maize DKC 3420 were cultivated at two locations: Budziszów, near Wrocław in southwestern Poland, and in Głuchów, near Rzeszów in the southeastern region, in the 2008-2010 growing seasons. For comparative analysis two additional non-Bt cultivars sprayed with a lambda-cyhalotrine insecticide also were included. To monitor the population density of soil surface-active invertebrates of the Staphylinidae family, 80 pitfall traps were used at each location. The average number of rove beetle populations in the Bt-maize habitat did not differ significantly from the number of beetles in the conventional ones. Significant differences in the number of beetles occurred only on individual dates. The variation in the number of beetles was probably caused by environmental factors, and therefore it cannot be related to the cultivar effect.