The electrochemical oxidation of thioselenanthrene (1c) in acetonitrile was studied by conventional and microelectrode techniques. Steady-state and cyclic voltammetry proved the occurrence of a DISP2 mechanism for the first oxidation signal. Controlled potential coulometry led to the formation of the corresponding selenoxide. The first electron transfer proceeds with a high heterogeneous rate constant (0.58 +/- 0.10 cm s(-1)), whereas a pseudo-first-order apparent rate constant of 8.87 +/- 1.11 s(-1) was computed for the chemical step, giving a half-lifetime of 78 +/- 10 ms for the cation-radical of 1c. In order to compare their cation-radical stabilities, similar measurements were also realized for phenoxathiine (1d) and phenoxaselenine (1e).