The effects of La3+ incorporation into a Pt/CeO2/Al2O3 catalyst were investigated by a combination of activity, temperature-programmed reduction (TPR), oxygen storage capacity (OSC), noble-metal surface area, and X-ray diffraction (XRD) measurements. Incorporation of La3+ ions into the Al2O3, before CeO2 is added, promoted higher Pt and CeO2 dispersions. The oxygen storage capacity was also higher in the presence of La3+. This is attributed to a combination of Pt and CeO2 particle-size effects and possible blockage of the reaction between Al2O3 and CeO2. The XRD data show that La3+ forms LaAlO3 with Al2O3 and prevents alpha-Al2O3 formation after various heat treatments.