The present work is a numerical simulation of laminar mixed convective in a two-dimensional parallel-plate channel provided with porous blocks of various shapes. The upper plate is thermally insulated while the blocks, heated from below, are attached on the lower one. The Brinkman-Forchheimer extended Darcy model with the Boussinesq approximation is adopted for the flow in the porous regions. The governing equations with the appropriate boundary conditions are solved by the control volume method. The influence of the buoyancy force intensity, the porous blocks shape going from the rectangular shape to the triangular shape, their height, the porous medium permeability, the Reynolds number and the thermal conductivity ratio is analyzed. The results reveal essentially, that the shape of the blocks can alter substantially the flow and heat transfer characteristics. In addition, it is shown that judicious choices of these parameters can lead to high heat transfer rates with a moderate increase of pressure drop. (C) 2009 Elsevier Ltd. All rights reserved.