The electrochemical properties of selenoxanthene, selenoxanthene-9-ol and selenoxanthone in non-aqueous and mixed media are investigated by voltammetry at rotating platinum and vitrous carbon disk electrodes, cyclic voltammetry, chronopotentiometry and constant potential coulometry. In “dry” acetonitrile selenoxanthene leads to selenoxanthylium cation. In the presence of water, selenoxanthene-9-ol is obtained. Further oxidation of selenoxanthene-9-ol gives the selenoxanthone which can be oxidized to the corresponding selenoxide. Influence of acids and bases is shown.