The Krkonoše Mts. in 70-ties and 80-ties of the XXth century were exposed to industrial emissions and recently are also threaten by more intense tourism and deforestation incident to new skiing areas. Bats are vulnerable to anthropogenic environmental changes in particular, so they are good bioindicator of habitats quality. We studied bat activity in different habitats of Krkonoše Mts. in three growing seasons (2012-2014). We aimed to determine (1) species diversity and flight activity of bat assemblages in selected habitats, (2) changes in flight activity and species composition throughout the season and in various altitudes, (3) the usage of small watercourses as potential flight corridors and (4) species diversity and bat flight activity in the forests with different management type. Bat activity was measured using echolocation calls units recorded by means of time expansion and automatic Lunar-2 detectors. Water surfaces, urban areas and forb-rich beech forests were the most species-rich areas, but only the forb-rich beech forests showed significantly higher bat activity. Increased activity and number of species were observed in the post-lactation period in most habitats, most notably at higher altitudes. Significant decrease in species diversity as well as in total bat activity was observed in acidophilous beech forests with increased altitude, while decrease in both variables in spruce forest was not significant. The flight activity over the watercourses was significantly higher than in control sites located outside of the corridors. We observed two pronounced periods of flight activity, i.e. emergence and return, over almost all studied streams. Despite different roost availability and food resources between the managed and unmanaged forests, no significant differences in species composition of bat assemblages or in total level of flight activity was found.