A study was carried out on the antioxidative activity of some selected plants: Hyperrium perforatum L., Oenothera depressa Greene, Foeniculum vulgare Mill., Pastinara sativa L., Pimpinella saxifraga L., Thymus marschallianus Willd., Artemisia maritima L. and Oenothera biennis L., Lard prepared by wet procedure served as the substrate. Using ethanolic extracts of plant materials, the best results were obtained with Thymus marschallianus Willd. and Oenothera biennis L. at 60°C. Antioxidative activity of powdered plants was studied on the Rancimat apparatus at 100°C, and increased induction periods were observed for all investigated samples. The extracts of Thymus marschallianus Willd. and Oenothera biennis L. were also investigated in the emulsion of linoleic acid and the course of oxidation was followed by measuring the decolouration rate of β‐carotene emulsion. In addition, the antioxidative activity of the Oenothera biennis L. extracts was studied at 60°C (determination of the peroxide number) and at 100°C (Rancimat) using lard as substrate. The synergistic action of citric acid in the combination with the Oenothera biennis L. extract was investigated under the same conditions.