Self-diffusion coefficients (D) of cesium ions in hydrous manganese dioxide have been determined radiochemically at different apparent capacities in aqueous and alcoholic solutions. The apparent capacity decreases in the order n-propanol > m,ethanol and is determined by both ion-solvent and ion-ion interaction. Self-diffusion coefficients (D) have been determined in all different media by using Paterson's approximation equation. Also, the effect of adding CsCl to the external aqueous or alcoholic hydroxide solution has been studied. (C) 2003 Published by Elsevier B.V.