The electrochemical oxidation of dibenzo(c,e)-1,2-diselenine (1a) in dry acetonitrile was studied by conventional and microelectrode techniques. Steady-state voltammetry and cyclic voltammetry proved the occurrence of an electro-chemical-electronic (ECE)-type mechanism for the first oxidation signal. The chemical step involves the reaction of the cation radical with residual water. The first electron transfer proceeds with a heterogeneous rate constant of 0.14 +/- 0.01 cm s(-1), whereas a pseudo-first-order kinetic rate constant of 20.7 +/- 2.8 s(-1) is computed for the chemical step, giving a half-life of 33 +/- 4 ms for the cation radical of 1a. A comparison of these two rate constants with those of dibenzo(c,e)-1,2-dithiin (1b), selenanthrene (2a) and thianthrene (2b) indicates that the electron transfer rate depends on the nature of the oxidized chalcogen, whereas the stabilization of the cation radical is also dependent on the geometry of the heterocycle.