The product composition and product buildup kinetics were studied for the isomerization reaction of alicyclic C-8 and C-12 epoxides yielding the corresponding ketones, including unsaturated ketones. A plausible mechanism of their formation was suggested for the case of the Lewis acid-catalyzed process. The reactivities of alicyclic epoxides were compared depending on their structure. The benefits of the preparation of individual ketones via the liquid-phase isomerization of corresponding epoxides were demonstrated.