Animal diet is reflected in the structure of the digestive tract. Some of the differences can be manifested in the thickness of individual layers or the number and type of glandular goblet cells that secrete mucose for digestion and protection. For this thesis, I selected five species of rodents that live in a sympatry in the karstic area of central Dalmatia, with the aim of determining if there are any histomorphometric and histochemical differences in the structure of the gastrointestinal tract, as a result of distinct diets of the species. Species that were included are Apodemus epimelas, Apodemus sylvaticus, Dinaromys bogdanovi, Eliomys quercinus i Glis glis. The histomorphometric results showed thicker esophageal keratenized epithelium and thinner esophageal outer muscular layer in carnovorous species, while species with highcalorie and easily digestible diets have thinner mucose layer of the glandular part of the stomach and thicker epithelium of the large intestine. Species whose diet contains toxic subtances showed specific adaptations in the thicknesses of certain layers. Histochemical analysis showed that carnivorous species have more acidic goblet cells in the small intestine, while granivorous species have more mixed ones. These results represent new data for included species and provide new insight into the existence of both differences between related species of rodents with distinct diets, and between species of different families but with similar diet, as between Apodemus genus and dormice species.