CeO2 promoted with either 1 wt% Pt or 1 wt% Pd was evaluated as a model system for passive NO x adsorber applications. According to NO x storage experiments conducted over the temperature range 80–160 °C, promotion with Pt resulted in higher NO x storage efficiencies than for the Pd-promoted material. However, for NO x storage at 80 and 120 °C, the latter released more NO x below 350 °C during temperature-programmed desorption in relative and absolute terms, the Pt analog releasing most of its stored NO x above 350 °C. DRIFT spectra showed that the use of Pd leads to preferential adsorption of NO x in the form of nitrites, while predominately nitrate formation is observed over the Pt promoted material. Overall, the use of Pd promoted CeO2 is preferred for low temperature NO x storage and release due to its ability to store NO x as thermally labile nitrites.