We examined the diet of Hyla arborea over its entire activity period (March to late September, 2004), and analysed a total of 585 adult samples. From the stomach contents we identified plant remains, shed-skin fragments, and animals. We identified a total of 2976 prey items, almost all of which originated from the terrestrial environment. Adult araneans and coleopterans were the most abundant prey items in the diet of the studied tree frogs. Some of the prey items become abundant in certain parts of the year (e.g. Homoptera, Lepidoptera larvae, Trichoptera). The dietary diversity index is high and exhibits seasonal changes. During the period of study an important seasonal change was observed in feeding intensity and in the type of consumed prey. Our results show that Hyla arborea has a broad dietary diversity which was expected as a consequence of exploiting the habitat both vertically and horizontally, possibly allowing access to a broader spectrum of prey.