In order to characterize the growth process of copper phthalocyanine (CuPc) thin films on vicinal Si(111) substrates, in situ spectroscopic ellipsometry (SE) and reflection anisotropy spectroscopy (RAS) were combined. The analysis of the in situ SE data implies a structural change occurring with increasing film thickness during growth. The ex situ SE data are fitted using a uniaxial model, and different out-of-plane molecular orientations are found: lying molecules on Si(111)-6 degrees and standing molecules on Si(111)-0.35 degrees. The average tilt angles of molecules relative to the substrate surface are calculated to be 41.5 degrees +/- 1.0 degrees and 81.1 degrees +/- 3.5 degrees, respectively. The in situ RAS spectra show that the optical anisotropy of CuPc/Si(111)-6 degrees is induced by the substrate anisotropy, and the strength of the RAS signal of CuPc films is proportional to the film thickness. (C) 2010 American Vacuum Society. [DOI:10.1116/1.3442797]