The redox behaviour of a Ce0.5Zr0.5O2 solid solution is investigated by means of temperature programmed reduction (TPR) and oxygen uptake measurements. It is shown that the introduction of ZrO2, into the CeO2 framework, strongly modifies the reduction behaviour in comparison to pure CeO2. Remarkably, in contrast to the CeO2, upon repetitive reduction-oxidation processes, the temperature of reduction of the solid solution decreases from 900 to 700 K. The reduction of NO by CO over metal-loaded catalysts is investigated and the role of support Ce3+ sites in the enhancing the NO conversion is discussed.