Substitution of thallium moiety in organothallium(III) compounds by selenocyanate is reported. Arylthallium (III) compounds react with KSeCN and CuSO4·5H2O or with Cu(SeCN)2 in dioxane to give aryl selenocyanates in good yields. Alkoxythallates of styrene react smoothly with KSeCN in methanol to afford 1-alkoxy-1-phenyl-2-selenocyanatoethanes almost quantitatively. The oxyselenocyanation of terminal