The catalytic properties of manganese porphyrins of the second and third generation and magnesium monoperoxyphthalate (MMPP) as oxidant have been studied in oxidation of cyclohexane or cyclooctane under mild conditions. We have found that the structure of manganese porphyrin has an influence on selectivity of the investigated reaction. Apart from main cycloalkanes oxidation products (alcohol and ketone), olefins and epoxides resulting from oxidative dehydrogenation of substrates in the course of reaction, were surprisingly found. This represents the first example of the oxidative dehydrogenation of cycloalkanes with MMPP as oxygen donor. The reaction mechanism is discussed and proposed. (c) 2006 Elsevier B.V. All rights reserved.