p-Nitrosodiphenylamine as a representative of nitrosoamine group was tested as a new reagent for the spectrophotometric determination of SO2. A mixture containing: p-nitrosodiphenylamine, formaldehyde, HCl, di-methylformamide and water was added to the aqueous test solutions of sulphites forming after 5 min, a blue complex with Λmax=675 nm stable for one hour. The Lambert-Beer law was obeyed in the 0 to 50 /ug SO2/cm3range. Molar absorptivity was equal to 2000 and the specific absorption was 0.062. The investigations should lead to search for other reagents from the nitrosoamine group suitable for this purpose.