This paper addresses the question of choosing the appropriate reactor length, wall thickness, and reactor opening size for self-sustained homogeneous combustion in parallel plate channels. First, the flame characteristics and stability of homogeneous combustion in micro-scale (< I mm) and meso-scale (> I mm) channels are studied, and the roles of heat recirculation and heat loss on the mechanisms of flame extinction and blowout are investigated. Based on these insights, the effects of reactor dimensions on flame stability are studied. Increasing the reactor length results in shrinking of the region of self-sustained combustion due to increased heat losses through the reactor solid structure. An optimum gap width in the range of similar to 600-1200 mu m (transition from micro- to meso-scales) provides the largest region of self-sustained combustion. Size effects are stronger for methane than for propane combustion. (c) 2006 Elsevier B.V. All rights reserved.