Ceria nanoparticles with controlled crystal orientations were fabricated via an oleate-modified hydrothermal method, which involved varying the molar ratio of oleate ions to cerium ions in the reaction solution ([Ole/Ce]) from 0 to 1. Quasicubic nanoparticles having primary {100} facets in addition to {110} edges were obtained for [Ole/Ce] values greater than 1/2. On the other hand, polyhedral nanoparticles surrounded by primary (111 facets appeared on nanoparticle surface at [Ole/Ce] smaller than 1/4. It was found that the bonding of the carboxyl terminals of the oleate ions with the cerium(IV) ions on the {100} surfaces balanced the electric charge of the stacked layers and that this is what resulted in the formation of cubic nanoparticles surrounded by (100} facets for [Ole/Ce] values larger than 1/2. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology japan. All rights reserved.