A new type of impactor with a cooled impaction plate was suggested by Lee and Kim (J. Aerosol Sci. 32 (2001) 107). The impactor performed well without coating material by using just the cooling impaction plate. However, the mechanism in the impactor was not elucidated by the experimental method. In this study, this kind of impactor specifically designed for capturing PM2.5 is presented. To understand the mechanism, two kinds of experiments were conducted. The experimental results show the condensation effect to be more effective than the thermophoresis effect in reducing the rebounce in the cooled plate impactor. Furthermore, this kind of impactor could be applied to PM2.5 classification. (C) 2003 Elsevier Ltd. All rights reserved.