Linear-sweep voltammograms were recorded on boron-doped diamond thin-film electrodes in K3Fe(CN)(6), K4Fe(CN)(6), quinone, and hydroquinone solutions; transfer coefficients and rate constants for anodic and cathodic reactions were determined. The reaction rates were compared to the diamond samples’ electrical characteristics measured by the impedance spectroscopy techniques. The polarization (faradaic) resistance of a redox reaction at its equilibrium potential was shown to be proportional to the specific resistance of diamond samples. Reaction rate constants for the quinone/hydroquinone system appeared to be significantly less than those for the Fe(CN)(3-/4-)(6) system.