Thin vacuum-deposited layers of metallophthalocyanines MePc (ca. 3 5 nm, Me = Cu, Ni, Co, Fe) on glassy carbon were investigated in water or acetonitrile with LiClO4 as supporting electrolyte. The potentiodynamic capacitance was measured by ac techniques at 1000 Hz in parallel to cyclic voltammograms. It served as a probe for interfacial MePc redox states. The results were confirmed by stationary impedance spectroscopy at a variety of constant potentials. In acetonitrile, cyclovoltammetric curves reveal a pseudocapacitive current step at 0.55 V (0.45 V) vs. she for CuPc and NiPc, more than 0.5 V ahead of the first intercalation peak for anions. The potentiodynamic capacitance is most sensitive to, and can be quantitatively correlated with, oxidation and reduction of the MePc surface molecules. Neutral CuPc behaves as a semiconductor electrode but it gives a common double layer capacitance of 15 muF cm-2. Beginning at 550 mV vs. she the capacitance increases to the remarkably large value of 305 muF cm-2. During the first anodic peak of the insertion of ClO4--anions at 1175 mV, the capacitance drops back to 180 muF cm-2 and decreases further to 45 muF cm-2 at 1600 mV at the end of the scan range. The back scan exhibits quite the same behaviour, though reversed, and its capacitance maximum is slightly broader and shifted to more negative potentials. The measurements for NiPc turned out to be very similar. The anodic dissolution of FePc and CoPc which occurs approximately 800 mV more negative than for CuPc and NiPc interrupts the initial rise of the capacitance for these electrodes. In aqueous electrolytes, other processes also contribute to the ac response so that the results must be handled in a more qualitative manner. The results are discussed in terms of electrochemical transformations of redox states at the surface of the solid metallophthalocyanines. The surface redox processes are well separated from the intrinsic redox processes, which are accompanied by insertion or release of anions. Characteristic high pseudocapacitances are found as expected.