The NOx-storage-catalyst is the most promising exhaust aftertreatment technology for spray-guided gasoline lean burn engines to eliminate nitrogen oxides under oxidising conditions. Due to the relatively cold exhaust-gas of this engine, the low-temperature activity of the catalyst is crucial in the NOx-storage process. Typically NOx-storage catalysts contain BaO as the major storage compound. If additionally Ceria is present in the catalyst an improved activity in the temperature range below 250°C can be obtained. One major aim of this work was was to clarify the influence of Ceria on the NOx-storage-cycle. Therefore, thermogravimetry and DRIFT-Spectroscopy were employed, both being in-situ methods capable of investigating a variety of technical relevant reaction conditions. These methods allow the detection of various species adsorbed on the catalyst surface, which was the main goal of this work. Furthermore, a study into their kinetic behaviour was performed as well. Results show that CeO2 is capable of adsorbing NO, NO2 and mixtures of NO/O2. Very much depending on the feed gas-composition different adsorbed species are formed during the storage process: nitrites, nitrates and hyponitrites. The different chemical pathways operating on the catalyst can be monitored by tracking those intermediates, e.g. direct oxidation of nitrit to nitrate can be followed on the catalyst surface by experiment. The findings clearly underline the key role of CeO2 in NOx-storage-catalyst applications. This is a direct consequence of its ability to store NO without prior oxidation to NO2. The onset temperature of formation of cerianitrate and -nitrite could be determined as being as low as 50 °C. Due to in the existence of two stable oxidation states (Ce(IV) and Ce(III)), a large number of reaction-pathways at the technical relevant low-temperature-regime are possible.