The effect of cooling water discharge from Skawina coal-fired power station on the quality of the Skawinka river water was presented in the paper. Hydrochemical research of both river and cooling water was conducted in 2012. Water for analyses was sampled from the river in 3 measurement points: 50 m above, 100 and 1000 m below cooling water discharge from the power plant. On the same dates cooling water samples were collected from the discharge channel. Selected physicochemical indices assessed in them comprised: the temperature, total suspended solids, dissolved oxygen, degree of oxygen saturation, electrolytic conductivity, total dissolved substances, pH, SO42-, Cl-, Ca2+, Mg2+, Na+, K+, PO43-, N-NH4+, N-NO2-, N-NO3-, Fe and Mn. The analyses revealed that cooling water discharge from the power station caused an increase in electrolytic conductivity and concentrations of dissolved substances and chlorides in the Skawinka water to the level exceeding border values for waters of purity class II. It affected a worsening of chemical state of the river from very good to good. Moreover, cooling water discharge raised water temperature and decreased dissolved oxygen content in the Skawinka river water, therefore worsening the cyprinid fish habitat condition. Statistical analysis showed that the discharge statistically significantly increased concentrations of all analysed salinity indices and nitrite nitrogen in the Skawinka water. However, it did not result from cooling water pollution by power generating technology applied by the power station, but was the effect of cooling the power station appliances with polluted water taken from the Vistula River, which after use is drained to the Skawinka.