It is shown that the efficiency of catalytic packages can be improved using two approaches. The monotone increase of the active component concentration towards the monolith outlet is shown optimal for minimization of the total active component loading at the preserved purification degree. To resolve the problem of achieving the maximal purification degree at a fixed quantity of the active component, it is preferable to concentrate the active component near the duct entrance. (C) 2004 Elsevier B.V. All rights reserved.