The reactivity of the peroxide adducts of manganese(III) Schiff base complexes towards several organic compounds was investigated by means of electrochemical methods and the results were interpreted in terms of molecular orbital calculations for both metal peroxide adduct and the organic compound. Based on these results, the importance of the electrophilic nature of the peroxide adduct and the electron distribution in the frontier orbital of organic acid anhydride moiety was stressed in order to explain the high reactivity between the two compounds.