In this work, we compare the effect of different types of thermal annealing on the morphological, structural and optical properties of Cu2ZnSnS4 (CZTS) thin films grown by reactive Pulsed Laser Deposition in H2S flow. Rutherford backscattering spectrometry, atomic force microscopy, X-ray diffraction, Raman spectroscopy and optical spectrophotometry data reveal dramatic increase of the band gap and the crystallite size without the formation of secondary phases upon annealing in N-2 at the optimized conditions. (C) 2015 Elsevier B.V. All rights reserved.