The flow directions of reactants in the anode and cathode channels have considerable impact on the dynamic responses of the nonhumidification polymer electrolyte membrane fuel cells (PEMFCs). In this study, the dynamic responses of nonhumidification PEMFCs using short-side-chain membranes are investigated with the variation in the flow direction of reactants using a three-dimensional transient simulation model. The dynamic responses of the cell voltages and local transfer currents are analyzed with the abrupt increase in the current density. Generally, the counter-flow cell exhibits a higher performance than the co-flow cell. During the load change, the co-flow cell experiences zero-power periods owing to the low cell voltage. Moreover, the counter-flow cell shows more uniform variation in the local transfer current and yields an even distribution in the overshoot compared to the co-flow cell owing to the higher membrane water content and the lower ionic resistance. However, the counter-flow cell results in a longer settling time compared to the co-flow cell owing to the large increase in the membrane water content. Overall, for the nonhumidification PEMFCs, the counter-flow cell is determined to be a preferred flow design owing to the higher performance and stability. (C) 2019 Elsevier Ltd. All rights reserved.