A hybrid model for accurate and computationally efficient simulations of the particle trapping characteristics of automotive flow-through catalysts is suggested in this paper. The new model is validated against the performance of a more elaborate, but computationally far more expensive model. In this hybrid model, the trapping of the smallest particles is predicted using a computationally efficient submodel that can also be used for screening of new catalyst substrate designs. It is shown here that this screening model is very accurate for particles smaller than approximately 50 nm. A number of different catalyst designs are evaluated and compared using the screening model. In particular, the performance of a promising channel design with porous obstacles is evaluated. This design could potentially give over 70% reduction of small soot particles without a substantial increase in the pressure drop. (C) 2010 Elsevier B.V. All rights reserved.