In recent years, the use of DeNO(x) catalyst on the substrate of a diesel particulate filter (DPF) has been extensively studied to increase the DeNO(x) functionality in a limited layout of vehicle application; the 2-way DPF/SCR is one example. The 2-way DPF/SCR inherently incorporates a wall flow type substrate in which the SCR catalyst is coated inside the wall. A number of studies have been performed on a conventional flow through type SCR reactor, so its behavior is relatively well known compared to the wall flow type SCR reactor. The purpose of this study is to identify characteristics of the wall flow type SCR reactor by comparison with the flow-through type SCR reactor. All the comparison studies are conducted by simulation models, which are thoroughly validated with experimental data for each type of reactor. Test cases include steady and unsteady operation and different space velocity and ammonia dosing conditions. Based on the results, SCR performance differences caused from flow characteristics are analyzed. Finally, non-dimensional performance parameters for each type of reactor are suggested. (C) 2012 Elsevier Ltd. All rights reserved.