Summer and autumnal activity patterns of juvenile and adult Dryomys nitedula were investigated in the wild using infrared motion sensor cameras. The study revealed that the forest dormouse is mainly crepuscular and nocturnal during the summer and autumn. Foraging activity started on average 8 min before sunset in June and shifted towards 26 min after sunset in September. The activity usually ended 40 min before sunrise independently of the season. The investigative activity around the nestboxes had three main periods: one between 20:00 and 22:00, one around midnight between 00:00 and 01:00, and a third one before sunrise between 4:00 and 6:00. Diurnal activity was also recorded but it occurred mainly in autumn and was restricted to the nestbox entrance; animals never switched nestboxes during the day if not disturbed. During the night activity, dormice used to investigate almost all nestboxes within their territory. However they showed preferences for only a few nestboxes which were used more frequently as daytime resting sites.