This study highlights the expansion of butterflies and macromoths occurring in southern Sweden. Recent changes in climate and habitat has been stressed as the main factors influencing changes in species distributions. Climate change implies an increase in temperature and some species are assumed to extend their northern ranges. In this study we compiled information about the first observations of butterflies and macromoths in the province of Scania in southernmost Sweden from 1973 to 2009. In total, 37 species have been found new to the province during this period. Noctuid moths dominate with 22 new species (59% of the total number), probably because they are more mobile compared with other families such as the Geometridae. Three butterfly species have been recorded new to Scania of which two have established reproducing populations and are widely distributed over Scania. Several of the new species occur irruptive and some species have only been found once. Of the 37 new species, approximately 16 have established local reproducing populations in the province. The increasing number of species occurring in Scania may be related to: i) increased temperature resulting in northward range shifts, ii) increased temperature leading to increased mobility, iii) an overall increased search effort resulting in more species being found, and iv) species naturally migrating and searching for new areas to establish in. It is likely that not just one single factor explains the changes in the butterfly and macromoth fauna of Scania but rather a combination of those mentioned above. It is important to monitor changes in species occurrence and abundance, especially when changes in climate and habitat are accelerating. Further studies are required to analyse consequences and patterns of species colonisations and range expansions. Probably, there are more lepidopteran species that risk extinction in Scania than the number of species that are colonising, but such patterns require careful monitoring to ensure that negative trends are detected before species have disappeared.