Light-induced structural changes of As-S glasses and films were probed both by macro FT-Raman and photon-energy dependent micro-Raman spectroscopy using different spectral composition of photoactive light: polychromatic or different wavelengths of laser radiation. The polychromatic illumination and thermal treatment leads to continuous decrease in intensity of characteristics vibrational modes of molecular or cage-like species like As4S4, As4S3, etc. Under laser illumination the picture is different, new observed features in the Raman spectra of As-rich As-S glass are related to transformations of As4S4 molecules: α(β)-As4S4 transform into pararealgar p -As4S4 form during laser illumination. The effectiveness of transformations depends mainly on photon energies used for irradiation, but the tendency to transform is observed for all used photon energies ranging from 1.65 to 2.54 eV. Experimental photon-energy dependent Raman spectroscopy used together with ab initio DFT calculations indicate that the mechanism of photo-induced changes in As-S glasses and films is defined by spectral width of illumination source (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)