A differentiation method of analysis of impedance spectra has been presented. It has been shown that the differentiation of impedance spectra extends analysis of the investigated process. On the basis of values : Z＇(f), Z "(f), (dZ＇(f)/d ln f)(f) and (dZ＇(f)/d ln f)(f) determined for frequency f(i), electric parameters have been resolved for a serial-parallel electric equivalent circuit. It has been stated that differential analysis allows determination of the functional dependency of electric elements of such an electric circuit from the measurement frequency.