The liquid-phase oxidation of 2-alkyl- and -cycloalkyl cyclohexanones by aqueous solution of hydrogen peroxide in the presence of molybdenum compounds and acetic acid has been studied. The oxidation of ketones was established to be proceeded through an intermediate stage of generating peroxocomplex of molybdenum. The additives of acetic acid lead to accelerating the complex formation and promotion of the selective oxidation of alkylcyclohexanones into the corresponding caprolactone. At the found optimum conditions the yield of ε-caprolactones (7-alkyl- and  -cycloalkyloksepan-2-ones) makes up 59–68%, the selectivity of the process while is  79–82%