The global kinetics of the reactions occurring during the selective catalytic reduction (SCR) of NO by NH3 over vanadia-based commercial DeNO(x) catalysts has been studied. The global kinetic model developed accounts for three chemical reaction pathways (Eley-Rideal and Langmuir-Hinshelwood type SCR and ammonia oxidation) occurring in this system and considers the effects of intraparticle diffusion phenomena. The model is applied to describe the global kinetics in the broad temperature range from 140 to 475 degrees C. New insight in the interplay between the processes occurring during SCR has been gained by considering the influence of the concentration of oxygen and water, the weak adsorption of NO alt low temperatures (T less than or equal to ca. 200 degrees C), the decrease of the NH3 coverage at high temperatures (T less than or equal to ca. 350 degrees C), the relevance of the Langmuir-Hinshelwood type SCR at temperatures below ca. 200 degrees C, the occurrence of NH3 oxidation as a side reaction at temperatures above ca. 300 degrees C, and the role of intraparticle diffusion.