A simple method was applied for preparation of Ce-doped ZnO nanostructures (mole fractions of Ce4+ ions are 0, 0.025, 0.05, 0.075 and 0.10) in water by refluxing for 3 h about at 90 degrees C. This method is large scale, mild and involve no templates, surfactants or additives. The prepared nanostructures were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis diffuse reflectance spectroscopy (DRS) techniques. The XRD patterns demonstrate that the nanostructures have the same crystal structure, and loading of Ce4+ ions does not change the structure of ZnO. The SEM images show that with increasing mole fraction of Ce4+ ions, morphology of the nanostructures changes from nanoplates to nanospheres. Photocatalytic activity of the nanostructures toward photodegradation of methylene blue (MB) was evaluated under UV irradiation. The results indicate that the nanostructures with 0.05 mole fraction of Ce4+ ions exhibit highest photocatalytic activity among the prepared samples. The influence of various operational parameters such as refluxing time, catalyst weight, calcinations temperature and pH of solution on the photodegradation reaction was studied. The optimum value for calcinations temperature was found to be at 400 degrees C. Moreover, the nanostructures have highest photocatalytic activity at solutions with pH between 5.4 and 9. (c) 2012 Elsevier B.V. All rights reserved.