In this paper we present a study of the optical properties of CdZnTe single crystal for low Zn concentrations at room temperature using photoacoustic spectroscopy and photoreflectance (PR) measurements. The photoreflectance measurements were carried out in order to determine the E-g value at room temperature of the CdTe sample to validate the criterion for the photoacoustic absorption measurements. The closed photoacoustic cell configuration (CPC) was used for the absorption measurements and, we use the knee method in the spectra for the energy band gap determination of CdZnTe as a function of the Zn concentration. The samples under study are commercial samples grown by the Bridgmann technique. X-ray diffraction was carried out in order to determine the Zn concentration of the samples and the FWHM of the diffraction peaks. The correlation between FWHM of the diffractograms and the photoacoustic absorption slopes shows that the absorption slopes could be associated with the crystalline quality of samples. (c) 2005 Elsevier B.V. All rights reserved.