In this work, the performance of two configurations of in situ zeolite-coated structured catalyst packings is treated. Just to demonstrate the reactor concepts, the catalyst packings were tested on a bench scale in the selective catalytic reduction of NO with excess ammonia. The performance of Cu-ZSM-5-coated ceramic slabs that were placed in a parallel passage array (PPR) was compared with a Cu-ZSM-5 monolith. Practical correlations are given for pressure drop, diffusion and the overall performance of the reactor. According to a simple model, the catalyst effectiveness factor of the PPR turned out to be 17%, whereas that of the monolith was 95%. The plate thickness and the spacing of the parallel plates proved to be of paramount importance for optimum catalyst efficiency. For practical evaluation and comparison with known NOx reduction units, more realistic reaction conditions should be chosen.