The lower jaws of 14 extant Palearctic mustelid species (290 specimens, Mustelidae, Carnivora) were analyzed through two-dimensional geometric morphometrics using 16 landmarks, in order to explore the relationship between mandibular size, shape and ecology within a comparative context. A principal component analysis and canonical variates analysis were performed on Procrustes fitted coordinates. PC and CV scores of the species means were also displayed with the phylogeny superimposed. Two types of the ascending ramus mandibulae are observed in mustelids - long and narrow one (sea otter-like), and short and wide one (badger-like). Both types of the ramus are present both in closely related species and in species with similar trophic specialization. Carnivorous mustelids (Mustela) differ from other trophic groups in relatively large carnassial, increased slicing area of m1, and high mandibular corpus under the canines. More omnivorous mustelids (Martes) have the longest and the thinnest lower jaw premolar region. But the lower jaw shape of Martes flavigula is closer to meat-eaters. The largest mustelids (Enhydra lutris, Meles meles, Gulo gulo) differ in lower jaw shape although they are all adapted to tough food but they have similar features as strengthened corpus under molar complex. Differences seem to be related with various food objects and with different ancestry and in the case of the wolverine with adaptation to predation. Piscivorous Lutra lutra is intermediate in all features and separate from the other groups. L. lutra with Mustela lutreola have the sloping forward ramus that with the posterior location of masseteric fossa possibly associates with fish consumption. The differences in mandibular traits of the studied species are partly determined both by their evolutionary history and ecological preferences.