The objective of this study was to determine the effects of various concentrations of water extracts prepared from the fresh or dry matter of lemon balm on Sitona lineatus L. and Aphis fabae Scop. behaviour. Beetles feeding intensity assessment was carried out by measuring the surface of feeds caused by S. lineatus. In determining the effect of extracts on A. fabae, the mortality of wingless female and aphid larvae was determined. In studies on the olfactory reaction glass olfactometer "Y-tube" and 4-armed arena olfactometer were used. The results of the experiment showed that water extract prepared from dry matter of lemon balm with 2% concentration limited the feeding of both female and male of S. lineatus. The increase in the mortality of the black bean aphid females and larvae was obtained only after applying the extracts from fresh and dry matter at highest concentrations. The evident deterrent reaction of odour substances obtained from the lemon balm plants towards the beetles of S. lineatus, could find the application in ecological farms via introducing the plant as accompanying crop to the main crops. The winged individuals of A. fabae did not react to the abovementioned factor.