Different structures and morphologies of SnO2 containing various amounts of ZnO were synthesized via a hydrothermal method (without any template), characterized by scanning electron microscopy and powder X-ray diffraction, and used for photocatalytic degradation of Congo red. The results revealed that using different ratios of Zn+2/Sn+2 affects the phase and morphology of the Zn2xSn1-xO2 compounds. This type of tailoring the morphology of SnO2 nanoparticles, ZnO doped SnO2 porous structure. ZnSnO3 flower-like, and Zn2SnO4 octahedrals was possible, by varying the Zn+2/Sn+2 ratio of 0, 1/10, 1/5 and 1/1, respectively. The formation mechanism of these products was proposed. Zn2SnO4 with octahedral morphology exhibited a significant enhancement of photocatalytic activity toward degrading Congo red, as compared to other samples. This could be attributed to enhanced oxygen vacancies and crystallite defects formed by substitution of Zn+2 in the lattice of SnO2, revealed in photoluminescence measurements. (C) 2010 Elsevier B.V. All rights reserved.