This review article is devoted to electrochemical investigations of symmetric organic diselenides and to their specific interactions with metals. Diselenides, as well as their metal complexes, are interesting from the biological, pharmacological and synthetic points of view. Special attention has been paid to their electroreduction on mercury electrodes in protic and aprotic solutions where mercury-assisted reactions proceed. Recent investigations of adsorption (in protic media) as well as mercury complex formation (in aprotic solution) were summarized and corresponding redox mechanisms presented. Results were compared with those of disulphides and ditellurides. The dynamic approach to the explanation of adsorption effects observed in protic media have been demonstrated. Electroreduction and oxidation of diselenides on solid electrodes and the electrosynthetic importance of electrochemically generated precursors have been discussed. The studies presented illustrate the significance of polarography and related techniques in mechanistic investigations of redox processes.