Investigations of the optical gap and the transport gap of two phthalocyanine (Pc) materials: CuPc and H2PC, deposited on hydrogen passivated Si were performed by means of spectroscopic ellipsometry and combined valence band photoernission and inverse photoemission. The optical gaps have found to be approximately the same value for both Pcs, namely 1.75 eV, while the transport gaps have values of (2.2 +/- 0.2) eV. Based on the values obtained the high similarity of these Pcs is discussed. (c) 2006 Elsevier Ltd. All rights reserved.