Several terpenoid d-hydroxy-g-lactones, g-hydroxy-d-lactones and their acetates were tested for feeding deterrent activity on three storage pest insects, the granary weevil beetle (Sitophilus granarius L.), the confused flour beetle (Tribolium confusum Duv.) and the khapra beetle (Trogoderma granarium Ev.). Homoterpenoid trans d-hydroxy-g-lactone 12 showed high, comparable with azadirachtin, activity against the adults of Tribolium confusum. Its cis isomer (17) was also very strong antifeedant but towards the larvae of. Trogoderma granarium. The results indicate that the feeding deterrent activity depends on the shape of the molecule of the tested compounds. The effect of the configuration of chiral centres present in the molecule as well as geometry of substituents at the lactone ring on the deterrency was observed. The antifeedant activity depends also on the developmental stage of the insects.