Differences in the resource use patterns of males and females of the spider crab species Maja brachydactyla Balss, 1922 and M. squinado (Herbst, 1788) from several geographic areas (three in the Atlantic and two in the Mediterranean) were studied through the analysis of stable isotopes of carbon and nitrogen in the exoskeleton of post-pubertal (adult) specimens. Results confirmed that males and females from the same population usually did not differ in δ15N values and hence foraged at the same trophic level. In contrast, females were usually enriched in 13C as compared with males from the same population, thus suggesting that females use shallower habitats than males before the terminal moult. The results reported here also indicate that stable isotop.