CeO2 has been prepared by thermal decomposition of CeCl3 . 7H(2)O at 550 degrees C. Commercial CeO2 has also been used for the sake of comparison. Powder samples have been characterized by X-ray diffraction and BET surface area determination. The point of zero charge (pzc) has been measured by potentiometric titration using KNO3 as a supporting electrolyte. Irrespective of the source, CeO2 has been found to possess the same pzc at 8.1 +/- 0.1. Titration data have been used to estimate the working surface and the inner layer capacitance. Depending on source, the surface charge density varies greatly, being much higher for CeO2 obtained by thermal decomposition. The apparent inconsistency has been attributed to difference in hydrophobicity of the oxide surface, a "porous" double layer being probably present on thermal CeO2 samples.