Abstract: The invention relates to a method for producing monocyclic ketones C4-C5. The inventive method is based on the reaction of a liquid-phase oxidation of monocyclic alkenes C4-C5 into corresponding cyclic ketones by nitrogen oxide or the mixture thereof with an inert gas. The process is carried out at a temperature ranging from 20 to 300° C. and a pressure of nitrogen oxide ranging from 0,01 to 100 atm. The inventive process ensures the high selectivity with respect to target products, the explosion safety at work and is promising for industrial use.