Abstract Extracts from savory (Satureja hortensis L.) and thymus (Thymus vulgaris L.) were obtained by supercritical fluid extraction, hydrodistillation, and Soxhlet extraction with benzene and ethanol. The composition of volatile compounds in the extracts was determined by gas chromatography, and the toxicity and antifeedant effects of the extracts on larvae of Colorado potato beetle were evaluated. Generally it is possible to claim that all extracts caused mortality in 24 h after their topical application. Significant differences between the particular extracts and plants were found. The most effective isolates were the essentials oils which showed the lowest LD50. The lethal dosages of 22 mg and 29 µg were determined for oil from S. hortensis and T. vulgaris, respectively, but the difference was not Significant (P < 0.05). The extracts of S. hortensis (SFE2 and SFE3) had similar efficiencies as the oils with lethal dosages of LD50 28 µg and 30 µg, respectively. Strong deterrent effects of all extracts against larvae were observed. In the no-choice test with leaf discs, the consumption of control food by the fourth instars larvae L. decemlineata was Significantly higher than the consumption of treated food in the treatment concentrations (P < 0.05). The AFI declined depending on the concentration.