Three-dimensional computational fluid dynamics (CFD) simulation of methane steam reforming (MS) reaction integrated with methane combustion (MC) in micro reformer was developed to compare the effects of parallel and checked arrangements on reformer performance. At base case condition, the checked and parallel arrangements provided a similar percentage of methane conversion which is about 68%, but hot and cold spots only appeared in the parallel arrangement. Furthermore, the flow direction (co- and counter current flow) in each arrangement was also investigated. The co-current direction provided slightly better results which is about 1% methane conversion in MS for both arrangements. By varying parameters, channel width was the only parameter which showed different results in both arrangements. The parallel arrangement showed higher performance when channel width was larger than 5 mm, but the cold and hot spots were obviously presented. Therefore, the checked arrangement with co-current flow is recommended for the reformer with larger than 5 mm channel width. For a smaller reformer, the reactor performances of both arrangements were similar with the difference of lower than 0.5% methane conversion in MS. Thus, the parallel arrangement with co-current flow is approved to apply in small channel micro reformer with simple flow distributor. (C) 2015 Elsevier B.V. All rights reserved.