Effect of several p- and p,p′-substituted diphenyl amines on the thermooxidative stability of styrene-butadiene rubber (SBR) has been studied using non-isothermal DSC measurements with the aim of exploring the relation between the structure of the compound and its antioxidative performance. The treatment of the experimental data was carried out by applying a new method based on a non-Arrhenian temperature function. In order to compare the stabilizing effect of the compounds, protection factors have been calculated from the oxidation induction times. The results achieved document that some functional groups in substituted diphenyl amines modify greatly the antioxidative performance. The groups having a positive mesomeric effect increase dramatically the antioxidant efficiency; the highest increase exhibited the nitroso group. On the other hand, the nitro group with the negative mesomeric effect is responsible for the loss of antioxidative properties. In general, the protection factors of the compounds depend on temperature.