The garden dormouse Eliomys quercinus, a native European rodent species, suffered a significant contraction in its geographical range in the last few decades. The species has disappeared from large parts of central and eastern Europe and is considered extinct in some countries. I reviewed the information available on the occurrence and distribution of the species in 26 countries where it was previously reported. Present and past introductions outside its native range were also summarised. The garden dormouse is considered extinct in Lithuania, Finland, and Slovakia, probably extinct in Belarus, and present with single populations in the Netherlands, Poland, and Slovenia; in Slovakia, however, monitoring is necessary to verify recent records. The species is rare and localised in Austria, Ukraine, Romania, and Croatia and is in regression in Germany, Flanders (Belgium), Czech Republic, Latvia, and Estonia. In 2015, the garden dormouse occupied 49% of its 1978 geographical range and 67% of its 2008 range. South-western Europe is the stronghold of the species; it is still common in large parts of Portugal, Spain, France, and Italy. However, there are indications that also in these countries, the species is locally declining. Present knowledge cannot explain the extensive regression of the garden dormouse's range in central and eastern Europe. Probably, it is the result of the interaction of different factors, acting locally and at a large scale, and related to specific ecological requirements of the species. There is a strong need for research to determine the reasons for the dramatic population and geographical range contraction of the garden dormouse. Meanwhile, it is important to monitor this species and to identify appropriate conservation measures.