The flow in a radial flow fixed bed reactor (RFBR) was simulated using computational fluid dynamics (CFD). There are four types of RFBR based on the axial direction of the flow in the distributing channel and the center pipe and the reactor radial flow direction. These types are known as CP-z, CP-π, CF-z and CF-π configurations. Flow in all four configurations was simulated. The model results showed good agreement with published experimental data. Results also showed that one of the π-flow configurations has always the most uniform axial flow compared to the z-flow configurations under the same conditions. Results also showed that if the ratio of the cross sectional area of the center pipe to that of the annular channel is less than one, the CF-π configuration gives the best uniform flow. For an area ratio larger than one, the CP-π configuration gives the best uniform flow.