The Authors report data about the presence of Disinfection By-Products (DBPs) and other halogenated compounds in drinking water samples collected in the areas of Modena and Parma (20 water supplies). Trihalomethanes, chlorite and chlorate (only in water samples treated with chlorine dioxide), and halogenated compounds were investigated. On the whole, trihalomethanes were evidenced in the 85% of the samples (n. 285) at low levels, while chlorite and chlorate were present in the 67% and 63% of the treated samples with chlorine dioxide (257 samples). Chlorite mean and median values were 225.70 microg/l and 136.75 microg/l respectively, ranging from 20 to 2000 microg/l. Chlorate concentrations were lower than chlorite: the mean value was 102.93 mg/l, while median level was 50 microg/l (range: 20-1500 microg/l). The high concentrations of chlorite and the wide range of values within each municipality plant in Modena and Parma suggest to investigate further in order to evaluate the human exposure in drinking water thoroughly.