The crystal plane of ceria plays an essential role in determining its catalytic oxidation properties. In this study, single-crystalline CeO 2 nanorods with well-defined crystal planes have been synthesized by a facile solution-based hydrothermal method. HRTEM studies reveal that the predominantly exposed planes are the unusually reactive {001} and {110} in the CeO 2 nanorods rather than the stable {111} in the irregular nanoparticles. Consequently, it is demonstrated that the CeO 2 nanorods are more reactive for CO oxidation than their counterparts, irregular nanoparticles. The present results indicate that catalysts with well-defined reactive sites may be “designed” because of the recent development of morphology-controlled synthesis of nanostructured materials.