Reactor performance of a trickle-bed reactor (TBR) concurrently under gas-liquid downward flow and that of a flooded-bed reactor (FBR) concurrently under gas-liquid upward flow was experimentally investigated under an elevated temperature and pressure (150degreesC and 1.0 MPa) for benzene hydrogenation. It was shown that the different hydrodynamics of TBR and FBR could result in quite different reactor behaviors, as typically observed from the temperature profiles along the reactor. The reason for this is because the present reaction is controlled by the supply of hydrogen in the liquid phase, thus external partial wetting of the catalyst pellets could increase the reaction rate. Moreover, the pronounced vapor pressure of benzene under the prescribed temperature would make the reaction remarkable over the non-wetted catalysts. Operation in the FBR is superior to the TBR, considering the operational safety. However, TBR should be considered when the catalyst partial wetting is negligible under liquid flow rates higher than 0.58 cm/s as shown in this work.