Feeding deterrent activity of some enantiomeric pairs of terpenoid lactones with the p-menthane system was tested against larval and adult Colorado potato beetle (Leptinotarsa decemlineata Say). The lactones were synthesized from optically pure isomers of pulegone and isopulegol. Monoterpene ketones and alcohols with the p-menthane system were weak antifeedants toward both Colorado potato beetle developmental stages. The introduction of the lactone moiety and an accessory functional group (hydroxy or ketone group) into the p-menthane skeleton increased feeding deterrent activity of the compounds. Our results show a correlation between chemical structure and antifeedant activity and indicated that the sensitivity of Colorado potato beetle to the tested lactones depends on the chiral centers configuration and the developmental stage of insects tested.