The effect of different processing routes on the microstructure of nanocrystalline ceria powder has been investigated. The nanocrystalline ceria is produced by solid state high energy ball milling (HEBM) and liquid state solution combustion synthesis (SCS) method. The liquid state route consists of a high temperature combustion reaction to form ceria from an aqueous solution of cerium ammonium nitrate (CAN) as an oxidizer and citric acid (CA) plus glycine (G) as mixed fuels. The powders have been characterized using techniques of X-ray diffraction (XRD), particle size analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The microstructural characterizations show that the particle size distribution of the ball milled ceria powder is much wider than that of ceria produced by the SCS. The scanning electron micrographs show that the ball milled ceria powders are compact and dense structure while SCS ceria powders are scattered and porous.