The structural and electronic properties of apigenin, luteolin, and taxifolin and their radicals were investigated at density functional level of theory employing the B3LYP exchange-correlation potential coupled with the 6-311++G** basis set. Results indicated that the presence of a dihydroxy functionality increases the radical stability through H-bonds formation and favors hydrogen atom abstraction. Bond dissociation energy and ionization potential were also determined in order to know if the antioxidant activity of these compounds proceeds via an H-atom or an electron-transfer mechanism.