Abstract The electrochemical behaviour of 7-substituted benzisoselenazol-3-(2H)-ones (BISAs) was investigated by voltammetry using a rotating platinum electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. The measurements were realized in “dry” neutral and acidic acetonitrile. Further oxidation od studied compounds gives the corresponding selenoxide. The role played by the protons during the reduction of this selenoxide has been demonstrated. The presence of a substituent in the 7-position of the benzisoselenazolin-3-one system strongly influence the values of the first oxidation potential. The nature of this interaction is discussed. A good correlation between thr first oxidation potential and the σ ortho Hammett coefficient is obtained. These results provide further evidence for the lack of association between the direct oxidation of BISAs into the corresponding selenoxide and the high (GSP-Px)-like activity of the 7-substituted BISAs.