The paper presents results of the experimental studies on combined ozonation and activated carbon adsorption processes at the Water Treatment Plant (WTP) at Cracow (Poland). The study focused on the selection of an appropriate location of an ozonation process within the treatment scheme and on the choice of activated carbon grade for adsorption. Analysis of process efficiency in the proposed technological configuration was performed based on some specific physico-chemical parameters, monitored in the effluents from the unit processes. It was found that introduction of ozonation resulted in better reduction of parameters describing organic contaminants. The authors proposed the process sequence: ozonation – sand filtration – GAC adsorption, based on previous laboratory results. The selected activated carbon demonstrated a better reduction of organic contaminants, expressed as: permanganate COD, dissolved organic carbon (DOC), UV absorbance and SUVA254.