The goal of this doctoral dissertation was to determine how the hydrothermal conditioning of tartary buckwheat grain, lactic acid fermentation and process of dough preparation and baking, influences availability and changes in the content of flavonoids, rutin and quercetin and antioxidant activity in baking samples of tartary buckwheat and hydrothermally treated (HT) tartary buckwheat. The content of rutin and quercetin in baking samples has been determined by HPLC method, while antioxidant activity has been determined by PCL and ORACFL methods. Hydrothermal conditioning, lactic acid fermentation and process of dough preparation and baking had an impact on content of total flavonoids and content and the conversion of rutin into quercetin in baking samples of tartary buckwheat and HT tartary buckwheat. The content of rutin decreased and the content of quercetin increased over the process of sour bread preparation in samples of tartary buckwheat and HT tartary buckwheat. Changes in antioxidant activity during the baking process were similar in tartary buckwheat and HT tartary buckwheat samples. We also found that the hydrothermal conditioning of tartary buckwheat grains did not affect the content of tannins in tartary buckwheat samples. We have established that tartary buckwheat sour bread with the addition of chia (90:10) had improved nutritional properties, which were expressed primarily in the increase of the content of n-3 (omega-3) fatty acids and an increase in total antioxidant activity. Our findings can be useful for development of breads with improved health-maintaining properties.