The yellow-necked mouse (Apodemus flavicollis), rodent of Muridae family, is common in the deciduous and mixed forests, gardens, parks from South Europre till Scandinavia. The purpose of research was to collect rodents from different areas of Scandinavia and to investigate genetic diversity of their. The back of A. flavicollis is dust-colour, belly is white, a mark between back and belly is quite clear. There is a band of yellow fur around the neck, between legs. Sometimes it is oval, sometimes like a strip. A. flavicollis tail is shorter than body and has 180 - 220 rings of exuviae. Juveniles are darker than adults and like a wood mouse [...]. During the international project „Molecular analysis of Ixodes ricinus and tick-borne disease in Norway and Lithuania“ small rodents were live-trapped with locally constructed wooden traps. All trapped rodents were marked, identified to species level, identified by sex and all attached ticks and fleas were removed. The ears, urinary bladder and spleen samples were taken from each rodent for further investigation. [...].