Quantum chemical calculations at the DFT/B3LYP, HF, and AM1 and PM3 semiempirical levels were employed to calculate a set of molecular properties for 41 phenol compounds with antioxidant activity. The significant molecular descriptors related to the compounds were the vertical ionization potentials (IPvs) and the charge on oxygen atom 7. The IPv has been calculated using Koopman's theorem IPv=-epsilon(HOMO(DFT)), IPv=-epsilon(HOMO(HF)) and as the difference of energy calculations for the corresponding cation and for the neutral form IPv(E(cation)-E(neutral)) obtained with the DFT/B3LYP method. The best model obtained showed not only the statistical significance but also predictive ability.