The objective of this study was to determine the effects of various concentrations of water extracts prepared from the fresh or dry mass of lemon balm on the feeding of Colorado potato beetle larvae in L2 and L4 stages. The extracts from the dry matter were prepared at the concentrations of 2%, 5% and 10% and from the fresh matter at the concentrations of 10%, 20% and 30%. The feeding intensity assessment was conducted by dipping leaves of potato in respective solutions of the extracts and determining the mass of food consumed by larvae, as well as the changes of larvae body weight. In the studies on the olfactory reaction of adult insects, a glass "Y-tube" olfactometer was used. The feeding by L4 larvae of Colorado potato beetle was effectively limited by the extract prepared from the dry matter of lemon balm with 10% concentration. The larvae at L2 stage turned out to be more susceptible to the effects of extracts – the extracts in almost all used concentrations limited the feeding of the studied pest. The body weight gain in L2 and L4 larvae of Colorado potato beetle were effectively limited by the extracts prepared from the dry plants of lemon balm in as low concentration as 5%. However, the effect of extracts prepared from the fresh matter of lemon balm plants was effective in limiting the body weight gain of L4 larvae at the minimum concentration of 20%, whereas for L4 larvae the effective concentration was 30%. The evident deterrent reaction of odour substances originating from lemon balm plants towards the females of Colorado potato beetle was found. The males did not react to the above-mentioned factor.