The EUROCAT SCR catalyst has been characterised by IR spectroscopic methods (transmission/absorption and diffuse reflectance techniques) by investigating its spectrum after different outgassing treatments, and the spectra of the surface species arising from adsorption of water (surface hydroxyl, groups), carbon monoxide, ammonia, pyridine, nitrogen monoxide, trimethyl berate and NO + NH3 coadsorptions. Additionally, Raman spectra and DR UV-Vis spectra have been reported after different outgassing treatments. The presence of Lewis and Bronsted acid sites has been discussed, as well as the evidence of different electronic states. A picture for the surface structure of the catalyst has been obtained. This picture is not significantly modified after extensive use of the catalyst in an SCR reactor for denitrifaction of flue gases from an incineration plant. (C) 2000 Elsevier Science B.V. All rights reserved.