Hibernation of bats is characterized by considerable changes in the oxygen supply during the torpor-arousal cycles. The purpose of this study was to examine the antioxidant defenses in tissues of the hibernating bats ( Eptesicus nilssonii , Myotis brandtii , and Plecotus auritus ), attempting to relate the tissue antioxidant protection with the ecophysiological characteristics of the studied species. We found that the superoxide dismutase (SOD) activity in the heart and the catalase activity in the skeletal muscle were higher in E. nilssonii than in P. auritus and in M. brandtii. In comparison with studied hibernating bats, P. auritus had the lowest activities of SOD and catalase in the heart. In addition, the level of glutathione was higher in the liver, kidneys, and muscle in M. brandtii than in the corresponding tissues of both P. auritus and E. nilssonii . We conclude that the differences in the mechanisms of adaptation to hibernation of bats are the result of various ecophysiological characteristics among species.