Nanocrystalline CeO2 particles doped in the range of 0-20% of Ca2+, La3+, and Zr4+ have been prepared from hydrothermal synthesis of nitrate solutions at 200 degrees C and the influences of the dopants on microstructure and optical properties of the nanoparticles have been investigated. The unit cell parameter is found to be modified by -0.39, +0.83 and +0.16% for doping of 20% Zr4+, La3+, and Ca2+, respectively. For each batch prepared, nanoparticles with a narrow size distribution of 5-15 nm have been obtained. A high-resolution transmission electron microscopy investigation reveals that these particles are single crystals mostly having hexagonal, square or circular two-dimensional projections. UV-visible spectra of doped powders exhibit shift of the absorption edge and absorption peak with respect to those of the undoped CeO2 particles and has been attributed to compensation of Ce3+ and decreasing crystallite size as result of doping. (C) 2011 Elsevier Ltd. All rights reserved.