Variation in habitat use was studied by radiotracking 11 polecats Mustela putorius in two wetlands in western France. Habitat selection showed a clear seasonality. Marshes were the most exploited habitat in spring while woods were mainly used in the coldest months and meadows were frequented in summer and winter. An analysis of scats showed that diet correlated with habitat utilization. The proportions of bank voles Clethrionomys glareolus, and meadow voles Microtus sp. were, respectively, related to the use of woods and meadows, while amphibians (mainly Rana dalmatina and Bufo bufo) were associated with marshes. Availabilities of rodents, assessed monthly by trapline success, were also significantly correlated to their occurrences. In contrast, no correlations were found between larger prey, such as brown rats Rattus norvegicus and rabbits Oryctolagus cuniculus, and any habitats or their abundance in the field. The occurrences of these prey and of some minor resources, such as shrews and birds, were correlated most with meteorological factors. The exploitation of marshes and amphibians increased when small rodents declined. Therefore, in the polecat, habitat selection was mostly influenced by trophic factors. Dietary diversity was greater in spring when food resources decreased, suggesting that polecats were optimal foragers. The study has emphasized that the polecat is a generalist feeder.