Cerium oxide with spheric, flowerlike and needle-like shapes has been synthesized by a simple microwave assisted method using diethylene glycole in mild conditions. The effect of reaction temperature on the crystal structure and morphology were thoroughly discussed. The structural evolutions and morphological characteristics of the nanostructures were investigated using X-ray diffractometery, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, TGA/DSC and BET analysis. By changing experimental conditions pure CeO 2 fluoritic phase or cerium formate with complex morphology were formed. High porosity CeO 2 nanostructures, retaining the end-reaction morphology, were readily obtained by calcination of cerium precursor. This simple and economic soft chemical method leads to nanostructured–micrometric aggregates of cerium oxide with high specific surface area suitable for catalytic applications.