This paper reports a comparative study on the anodic oxidation of 50 mg/L Acid Orange II in the presence of different supporting electrolytes. Experiments have been performed with a batch recirculation reactor containing one-compartment cell equipped with boron-doped diamond anode and Pt cathode. Specifically, the effect of cation is examined among a series of inorganic salts while keeping the anion constant. The results show a significant influence of the applied current density and also of the electrolyte cation on the efficiency of the treatment. in addition, the evidences from electrochemical measurements are used to better clarify the different sequences recorded. (c) 2009 Elsevier B.V. All rights reserved.