High-resolution spatial profile sampling has recently gained increasing attention for characterizing the performances of catalysts supported on structured monoliths [1-4].In particular, collecting spatially-resolved gas-phase concentration profiles by applying suction probe techniques has provided novel insights into reaction mechanisms and represents an important tool for optimizing catalyst design.However, the significance of the probing techniques impact on the measured data is not clear.In the present work, this effect is investigated by means of CFD simulations.