Abstract The decomposition of a number of chlorophenols (CPs), namely 2-CP, 2,4-dichlorophenol and 2,4,6-trichlorophenol, has been studied in aqueous solution by UV-catalyzed oxidation with H 2O 2 under UV radiation emitted by a 125-W medium pressure Hg lamp in an immersion well-type quartz photoreactor, and the organic-bound chlorine has been converted into the environmentally harmless inorganic chloride. For oxidant/CP mole ratios between 1:1 and 16:1, the reaction kinetics were modeled and the corresponding rate constants found by periodically measuring the remaining CP, hydrogen peroxide and converted chloride in solution. A theoretical model for the degradation pathway is proposed expressing the rate as a linear function of the concentrations of CP and oxidant. The rate constants for the pseudo-first order approximation of the CP degradation were compared. H 2O 2, when combined with UV, is an effective photoactivated oxidant. The photodegradation order in terms of the initial rate of CPs destruction was: Cl 3·Ph≥Cl 2·Ph>Cl·Ph.