The objective of this research is to asses the impact of the addition of H2O, SO2, and both in the SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths. The sulphated catalyst keeps a 100% conversion and total selectivity to N-2 in the low temperature range, i.e. 473-500 K. when either H2O or SO2 is added to the gas feed. However, a decline of steady state conversion and selectivity occurs when both H2O and SO2 are added simultaneously because H2O speeds up the deposition of ammonium sulphate salts. This decrease of catalyst performance is reversed when the reaction is carried out under dry conditions at temperatures higher than 473 K but not at lower temperature (453 K). Thus, the catalyst has demonstrated to be a good candidate for the SCR of NO at low temperatures even in stack gases containing traces of undesired components. (c) 2006 Elsevier B.V. All rights reserved.