Profiles of diffusion flames in plane-parallel packed beds were examined theoretically and experimentally. In the analyses, the flame sheet model taking into account mass dispersion within a packed bed was developed to quantify the effects of several system parameters on the flame shape and flame height in a packed bed. Moreover, experiments for methane-oxygen diffusion combustion in a plane-parallel packed bed of alumina spheres were made to estimate actual flame shapes in the packed bed from photographs of the upper surface of the packed bed and to examine the validity of the flame sheet model. (C) 2004 Elsevier Ltd. All rights reserved.