Flow over a thin strip is one of the major experimental configurations in the study of catalytic combustion. 1D laminar stagnation-flow models are generally employed to investigate the catalytic combustion characteristics in this experimental configuration. In this study, a 2D Cartesian model is developed to examine the conditions under which 1D models are applicable. The results show that the 1D model is only appropriate in the experimental configurations with a length-to-width ratio less than 1 to 3 (depending on the flow conditions). The 1D model failed because of the neglecting of transverse diffusive mass transfer (at Re < 30) and of the oversimplified convective mass transfer (at Re > 60). The calculations of the 1D and 2D models are also compared against the OH measurements performed in a typical stagnation-flow reactor with a length-to-width ratio of 16. The results show that the computations of the 2D model are in better agreement with the experimental data. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved.