Flow distribution in four possible configurations, CP-z, CP-π, CF-z, and CF-π, of a radial flow reactor is investigated using computational fluid dynamics (CFD). The CFD models are validated using published experimental data. It is found that one of the π-flow configurations always has the most uniform flow distribution. Results show that the ratio of the center pipe cross-sectional area to that of the annular channel has a significant effect on the flow distribution. For a ratio less than one, the CF-π configuration gives the most uniform flow, while the CP-π is preferred for a ratio larger than one. It was also shown that the uniformity of the flow distribution is enhanced by lowering the porosity of the center pipe and that of the bed. To ensure good distribution, partial blockage of the center pipe must be avoided.