From 1999 to 2013, a long-term capture-markrecapture study was carried out in a local population of the forest dormouse, Dryomys nitedula, in a mixed forest patch surrounded by unsuitable habitat in Lithuania. Many aspects of this population's ecology are different from those situated elsewhere. In the population, the activity period of D. nitedula was the shortest in the entire range (about 4.5 months, late April to early September). Breeding season was early and short, most litters were born in early June, and the average litter size (3.2 ± 1.1 young) was very small. The average densities of the local population were 4.5 ± 1 and 6.7 ± 2.1 ind./10 ha after and before hibernation, respectively. The abundance of the local population was stable, and the sex ratio was approaching 1:1 among adult individuals, except in the first years of the study when abundance was higher than usual and the sex ratio was female-biased. One-year-old dormice comprised about 49% of the population, while 2-, 3-, and 4-year-olds and older accounted for 24%, 14% and 13%, respectively. Maximum life span was 6 years in one female and maximum body weight recorded before hibernation was 57.5 g in an adult male.