Studies were made of the shape, volume and depth below ground level of hibernation cavities used by free-living and captive edible dormice, Glis glis (Linnaeus, 1766). Most of the cavities (77 out of 83) were occupied by a single animal. Sixty of them had a characteristic oval shape and were analysed in detail. The volume of cavities in free-living dormice ranged from 429 cm3 to 1174 cm3 (median = 670 cm3, Q1 = 605.5 cm3, Q3 = 855 cm3, N = 17) and in captive animals from 293 cm3 to 2211 cm3 (median = 837 cm3, Q1 = 571 cm3, Q3 = 1055 cm3, N = 43). No correlation between body mass of hibernating dormice and volume of their cavities was found. A tendency for male cavities to be larger than female ones was evident, although the differences were not statistically significant. Comparison of volumes of cavities made by free-living versus captive dormice, as well as captive adults versus subadults also did not reveal significant differences. Cavities of free-living dormice were found between 18 and 70 cm underground (median = 30 cm, Q1 = 25 cm, Q3 = 40 cm).