A comparative cyclic voltammetric study of hydrogen and deuterium sorption into a thin layer palladium electrode from acidic and basic solution containing cesium cations has been performed. Cesium has been detected in palladium electrodes by neutron activation analysis after hydrogen electrolysis from 0.1 M CsOH and it has a marked influence on the alpha- to beta-phase transition only in basic solution. The results obtained are compared with those of solutions containing lithium cations [A. Czerwinski, Electrochim. Acta, 39, 431 (1994)].