Buckwheat contains high biological value proteins, unsaturated fatty acids-rich lipids, vitamins B₁, B₂ and B₆, and polyphenols showing a high antioxidative activity; owing to those components, it is a valuable raw material for foods with health benefits. The objective of the study was to determine the content of polyphenols in and the antioxidative activity of extracts made from buckwheat grains of the Polish varieties and from by-products produced while processing buckwheat into groats. A synthetic antioxidant BHT was used for comparative purposes. Two Polish buckwheat varieties were studied: ‘Kora’ and ‘Panda’ (Fagopyrum esculentum Moench L.). The extraction was performed using acetone, methanol, and water, at a temperature of 20 ± 2 ºC, during 24 hours. The level of total phenolic compounds was determined spectrophotometrically using a Folin-Ciocalteu reagent and a gallic acid as a standard. Antioxidative activity of extracts was analyzed in the presence of linoleic acid with the incubation period of 19 hours and using a DPPH^• stable radical scavenging method (2,2-diphenyl-1-picrylhydrazyl), under the Oxidograph assay conditions. Methanol extracts were characterized by the highest content of phenolic compounds (ca. 63 – 68 mg GAE/g d.m.), the next highest contents thereof were reported in the acetone (ca. 44 – 48 mg GAE/g d.m.) and water extracts (ca. 25 – 30 mg GAE/g d.m.). The buckwheat grains of ‘Kora’ variety were characterized by a slightly higher content of polyphenols and a similar antioxidative activity compared to the ‘Panda’ variety. The highest content of total phenols was found in the methanol extracts of buckwheat hulls of ‘Kora’ variety: 140.4 mg/g d.m. Also, those extracts were characterized by the highest antioxidative activity (98.8 %). In the emulsion system, the water extracts were characterized by a high antioxidative activity as were the methanol extracts. The extracts produced showed a weak stabilizing effect on rapeseed oil in the Oxidograph test.