The present study compares the photocatalytic decolorization ability of CuO as supported onto both micronized zeolite X (CuO/MX) and zeolite X nano-particles (CuO/NX) toward aqueous mixture of Methyl Orange (MO) and Methylene Blue (MB). Both photocatalysts were characterized by XRD, SEM, BET, FT-IR and DRS. The progress of the photodecolorization of the proposed mixture was monitored using UV-vis spectrophotometer. The decolorization of dyes was systematically studied by varying the experimental parameters in order to achieve maximum decolorization efficiency. Application of the Langmuir-Hinshelwood kinetics allowed calculating the photodecolorization rate constants. CuO/NX was more efficient than CuO/MX and also, MO was more degraded than MB. The reusability of the photocatalyts was also tested and the decolorization activities of 90% and 88% were respectively obtained for CuO/NX and CuO/MX after four recycles. (C) 2014 Elsevier B.V. All rights reserved.