The work presents small signal capacitance (SSC) spectra within the 25 Hz-1 MHz range and direct current-voltage curve obtained on indium tin oxide/palladium phthalocyanine (PdPc)/Al. The system exhibits strong current rectification, but SSC spectra do not bring any evidence of the presence of Schottky barrier at Al/PdPc interface. The reverse current seems to result from electrochemical processes. The problem how dielectric polarization processes which can occur in organic layer can be distinguished from relaxation of charge carriers in SSC spectra of organic devices is considered. Relation between SSC spectra and direct current-voltage curve is discussed. (C) 2010 Elsevier B.V. All rights reserved.