Effect of nine new derivatives of dihydroquercetin (taxifolin) on the viability of cultivated normal and tumor cells, their antioxidant activity, and interconnection of the antioxidant activity with the chemical structure have been studied. Among these dihydroquercetin derivatives, the maximum antiproliferative activity on the model of rat fibroblast culture exhibited KN-2, KN-4, KN-7, and KN-8 compounds, while KN-7 and KN-8 compounds also showed maximum activity on the model of MCF-7 tumor cell culture (human breast cancer). The maximum general antioxidant activity was observed for the native dihydroquercetin and KN-8 compound. There is a strong correlation (with a correlation coefficient of 0.93) between the antiproliferative effects of dihydroquercetin derivatives on murine skin fibroblasts and MCF-7 cells (human breast cancer).