Dams represent one of the most significant human impacts on river systems. The aim of this work was to determine the impact of hydroelectric power plants (HPP), dams and reservoirs on rivers in the Adriatic basin of Croatia. For all the rivers of the Adriatic basin, which have dams and HPP along their course, a cartographic analysis was carried out using 1:25000 scale maps. The lengths of the river reaches were determined without the influence of the HPP (usually upstream of the reservoir), as well as the river reaches that were converted into the reservoir (direct loss of river habitats) and the river reaches downstream of the reservoir (hydrological impact). In the basin of 12 rivers with a total river length of 472 km, the construction of 16 reservoirs transformed a total of 77 km (16%) of river length into reservoirs, 134 km of river length (28%) is under the hydrological influence of HPP, and 50 km (11 %) is under extreme hydrological influence (river constantly or occasionally dries up). The rivers of the Adriatic basin in Croatia have been significantly altered due to the construction of dams and reservoirs for the needs of 11 large (>10 MW) and six small (>10 MW) hydropower plants. The remaining preserved parts of the course of the rivers of the Adriatic basin, especially those on which there are no other impacts (e.g. water abstraction), need to be protected from further negative impacts.