SnO2-based sensors present strong interactions with NOx-containing atmospheres. For this reason, it is fundamental to identify the nature of the adsorbed species resulting from the interaction of NO and NO2 with the tin oxide surface. This aspect has been studied in literature by Temperature Programmed Desorption (TPD). To state more precisely structures of adsorbed species, we link TPD with Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS). Concerning NO2 adsorption, DRIFTS experiments indicate the formation of monodentate nitrato species at room temperature. By increasing the temperature, a conversion of adsorbed species is observed. The nature of surface groups is discussed. In the presence of hydroxyl groups (two different OH groups are evidenced), the formation of hydrogeno nitrates is detected.