In the present work diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy is applied to study the adsorption of NOx at 300-500 degrees C in different atmospheres on gadolinium-doped ceria (CGO), an important material in electrodes investigated for electrochemical NO removal. Furthermore, the effect on the NOx adsorption when adding K2O or BaO to the CGO is investigated. The DRIFT study shows mainly the presence of nitrate species at 500 degrees C, whereas at lower temperature a diversity of adsorbed NO species exists on the CGO. The presence of O-2 is shown to have a strong effect on the adsorption of NO, but no effect on the adsorption of NO2. Addition of K2O and BaO dramatically affects the NOx adsorption and the results also show that the adsorbed NOx species are mobile and capable of changing adsorption state in the investigated temperature range.