This study comprehensively investigates the dominance of various structural factors in a passive air-breathing DMFC by means of orthogonal array analysis (OAA). Two membrane types, two assembly patterns of the diffusion layer and two open ratios of the current collector are prepared. Three target variables are selected as the performance indexes including the maximum power density (MPD), limiting current density (LCD) and open circuit voltage (OCV). The range analysis (RA) method and effect curves (ECs) are used to characterize the OAA data. The RA results demonstrate that the current collector and diffusion layer combine to dominate the values of MPD and LCD in a wide range of methanol concentrations from 0.5 to 8 M. The dominant structural factors related to the value of OCV at different methanol concentrations are also explored. In addition, the effect curves show that a medium methanol concentration like 2 M generally promotes higher values of MPD and LCD, while a relatively lower methanol concentration like 0.5 M benefits a higher value of OCV than others in a general statistical sense. (C) 2010 Elsevier Ltd. All rights reserved.