The electrochemical reduction in dimethylsulphoxide of five mono- and diacetyl derivatives of diphenylsulphide and diphenylsulphone was investigated by means of cyclic voltammetry, ESR spectroscopy and optical spectroscopy. In all cases the first reduction step corresponds to a reversible monoelectronic transfer and leads to the formation of an anion radical which is stable enough to be detected by in-situ ESR and optical spectroscopy. The electronic structure of the anion radical and the follow-up reactions are determined by the acetyl substituent and only influenced slightly by the degree of oxidation of the sulphur atom. Semi-empirical MO calculations in the frame of the AM1 method provide a good description of the main trends observed experimentally.