This paper presents an analysis of stormwater quality from urbanized catchments (roads) and the effects of its treatment with retention and retention-infiltration basins. The research was carried out on two types of objects: a retention-infiltration basin in Kraków and three reservoirs by Road No. 4 near the city. The following pollution indexes were analyzed: COD, total suspended solids and mineral suspended solids, reaction, chlorides, phosphates, and ammonium nitrogen. The research proved that COD, suspended solids, and chlorides played a crucial role in the quality of stormwater from the roads. The analysis of the main components of stormwater samples from the reservoir showed that the processes were determined by three major components that provided almost 93.0% of the total information on interactions between pollutants.