An experimental design was done to study the effects of initial support morphology (porosity and BET surface area) and catalyst synthesis conditions (vanadia loading and calcination temperature) on performance of DeNO(x) catalysts. The results show that final catalyst surface area is independent of initial support morphology, but NO conversion is sensitive to the initial state of the support as well as to synthesis conditions. Conclusions challenge the convention that catalyst performance benefits from high support surface area. The findings also teach that increased porosity improves catalyst stability against sintering. (c) 2006 Published by Elsevier B.V.