The AC electrical characterization of Au/porous silicon/p-Si structures is presented. The Porous Silicon layers were prepared by electrochemical etching in p-type silicon substrates. The AC electrical measurements capacitance – conductance – frequency were performed from 5 Hz to 10 MHz, at room temperature in the DC range of ± 2 V. We studied two structures types; first a conductor type Au/PS/Au and second diode type Au/PS/p-Si/Al. We have obtained the parameter fitting values according an electrical model circuit in AC corresponding to the sample fabricated. In the electrical characterization the low frequency phenomenon, the geometric capacitance and the depletion capacitances presented in the structures were determined.