The oxidation of cyclohexene and its methyl derivative with hydrogen peroxide in the presence of a catalytic system based on polyoxomolybdate and cobalt(II) bromide has been studied. It is found that epoxidation and oxidative dihydroxylation of cycloolefins without changing the initial structure are the main reaction routes at a temperature of 50-60 degrees C, a duration of 5-7 h, and a substrate:oxidizer molar ratio of 1:2. The process further proceeds by oxidative decyclization of epoxide and diol into aliphatic oxyaldehydes and oxyacids under more harsh conditions (T = 70-80 degrees C, reaction duration of 20-24 h, molar ratio of cycloolefin:oxidizer 1:4).