The infrared spectral performance of the NxOy species observed on oxide surfaces [N2O, NO-, NO, (NO)(2), N2O3, NO+, NO2-(different nitro and nitrito anions), NO2, N2O4, N2O5, NO2+, and NO3- (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N-2, H-, and C-containing nitrogen oxo species, C-N species, NHx species) are also briefly discussed. Some guidelines for spectral identification of NxOy adspecies are proposed and the transformation of the nitrogen oxo species on catalyst surfaces are regarded.