Nanocrystalline ceria was prepared by hydrothermal technique using formic acid as the solvent.XRD analysis confirmed the cubic phase of ceria with fluorite structure and TEM analysis revealed spherical particles having a narrow size distribution.IR and XPS analyses indicated no detectable water,formic acid or NO - 3 ions.The quantum size effect of nanocrystalline ceria had also been studied with PA spectroscopy.