The effects of the addition of rhodium to CeO2(70 wt%)-ZrO2 support on hydrogen reduction of the support have been studied. The effects change significantly with an increase in calcination temperature of the support. The lattice constant of CeO2-ZrO2 decreases with an increase in calcination temperature. The correlation curve between the lattice constant and calcination temperature as well as that between crystalline growth and calcination temperature has an inflection point at 900 degrees C. Thus, the structure of the CeO2-ZrO2 solid solutions depends on the calcination temperature. In particular, the structure changes significantly at 900 degrees C and calcination at 900 degrees C shows a maximum amount of surface oxygen-deficient sites catalyzing N2O decomposition. Moreover, the reduction extent at 400 degrees C is directly proportional to rhodium concentration per unit surface area in addition to the considerable structure change of CeO2-ZrO2. Hence, the localization and/or aggregation effect of rhodium particles also contributes to the reduction creating surface oxygen vacancy.