The seasonal activity of the common dormouse Muscardinus avellanarius was studied in three different habitat types of central Italy: a deciduous beech wood dominated by Fagus sylvatica (Cimini Mountains), and a deciduous oak woodland with Quercus cerris and Q. pubescens and an evergreen wood dominated by holm oak Q. ilex, both along the central Tyrrhenic coast. In each site, 50 nest-boxes were fixed to trees and were monitored monthly for 2 years (May 1998–April 2000). In the beech wood site, the species showed an annual biological cycle similar to that described for populations of central and northern Europe: dormancy in winter, from the first 10 days of November to the end of December; end of hibernation in the first half of April; reproduction between May and July. On the contrary, in the two coastal sites, nest-boxes were occupied from October to June, and the breeding period was in autumn, showing that a winter dormancy phase is absent, probably owing to the mild winter. On the other hand, no dormice or new nests were observed in nest-boxes in summer suggesting that a dormancy phase occurred in summer, probably owing to dry climatic conditions. Two patterns of biological cycle therefore emerged from the results: a temperate pattern in beech forest with winter dormancy and spring reproduction, and a Mediterranean pattern in coastal habitats with autumnal reproduction, winter activity and summer dormancy.