Use of biomass as an alternative to fossil fuels has achieved increasing interest since it is considered neutral regarding CO2 accumulation in the atmosphere. The by far most energy-efficient use of solid bio-resources in energy production is combustion in combined biomass and coal or oilfired power plants. However, in this operation traditional catalysts exhibit significant deactivation within relatively short time. The main reason for this deactivation is the presence of a high amount of potassium compounds, which act as poisons for the catalyst. Therefore, there is a need for development of new alternative catalysts that are more resistant towards poisoning with potassium. Vanadia-based catalysts supported on traditional and tungstated zirconia has been prepared and tested in selective catalytic reduction of NO with ammonia. All prepared catalysts were characterized using N2-BET, XRD, and NH3-TPD methods. The influence of calcination temperature of zirconia modified with tungsten oxide on the textural characteristics, acidity and catalytic performance was studied. The resistance of the catalysts towards model poisoning with potassium was found to depend dramatically on the crystallinity of the zirconia and on the surface acidity. Vanadia supported on tungstated zirconia calcined at 700 8C revealed superior catalytic performance and resistance towards alkali poisoning in comparison with a traditional catalyst. The improved poisoning resistance of the samples based on tungstated zirconia can be related to the fact that a significant part of potassium on the surface of the catalyst preferentially interact with strong acidic sites now present on the support, thereby preventing vanadium species from poisoning and leaving them available for the catalytic cycle.