Dormice are primarily nocturnal, but some are active during the day. Most species are arboreal and agile climbers, but some thrive in treeless, arid regions. Some are adept rock climbers, reportedly able to scale vertical rock faces and even walk upside down under rock ledges. Dormice construct globular nests (nest) in trees, bushes, rock crevices, and burrows and among tree roots; some also utilize abandoned bird or squirrel nests and, occasionally, active beehives. Their diet consists of fruit, nuts, insects, spiders, bird eggs and nestlings, and small rodents—even other dormice.

Dormice are found in Eurasia from western Europe to eastern China, in southern Japan, along the Mediterranean margin of North Africa, and throughout sub-Saharan Africa. They live in a diverse variety of habitats from boreal (boreal forest) and deciduous forests to orchards and tropical rainforests, through open country broken by scattered clusters of trees and shrubs to clay and sandy deserts and rocky, dry plateaus. Species living at temperate and boreal latitudes accumulate body fat in the fall and hibernate during much of the winter, rousing occasionally to eat food that they have stored. Tropical and desert species experience periods of torpor but not hibernation.

Dormice are not “true” mice (family Muridae); they are the only members of family Myoxidae, but their relationship to other rodents is not clear. Dormice have been allied with two different major groups: the squirrel-like rodents (suborder Sciuromorpha) and the mouselike rodents (suborder Myomorpha). In reality, the closest living relatives of dormice are unknown. The dormouse family has a long and diverse evolutionary history from the Early Eocene Epoch (54.8 million to 49 million years ago) in Europe and Asia and from the Middle Miocene Epoch (16.4 million to 11.2 million years ago) in Africa; this history produced today's living forms as well as numerous extinct species in 36 genera that are represented only by fossils.