Effect of the solvent nature on the kinetics of photoreduction of substituted benzoquinones in the presence of hydrogen donors has been studied. It has been found that the effective photoreduction rate constant (k H) for quinones decreases with an increase in solvent polarity. For the 3,6-di-tert-butylbenzoquinone–1,2-N,N-dimethylaniline pair, the dependence of ln k H on the difference of the reciprocals of optical and static solvent permitivities (1/ε ∞–1/ε0) is stepwise with a break point corresponding to CH2Cl2. A similar relationship lnk H = f(1/ε ∞–1/ε0) is observed for the p-chloranil–mesitylene pair. In the study of the photoreduction kinetics for a series of seven o-benzoquinones in the presence of p-derivatives of N,N-dimethylaniline in CH2Cl2, it has been found that the dependence of k H on the free energy of electron transfer (ΔG e ) has a maximum for the 3,6-di-tert-butylquinone-1,2–N,N-dimethylaniline pair at ΔG e = 0.11 eV.