A promising approach to process intensification of catalytic gas/liquid reactions is the use of mini structured reactors such as honeycomb shaped fixed beds with parallel flow channels. For additional output increase the flow channels can additionally be filled with spherical catalysts that have about the same diameter as the channels. An experimental study was made on monolith catalysts and sphere-packed monolith catalysts using as example the hydrogenation of α-methylstyrene. Four different fixed beds were considered. They were monolith catalyst with empty flow channels; inert monolith carrier filled with catalyst spheres; monolith catalyst filled with catalyst spheres; and typical trickle bed catalyst. For each fixed bed the optimal hydrodynamic conditions with respect to gas and liquid throughputs were determined for a maximum change in mass velocity. The combination of monolith catalyst and bead catalyst doubled the reactor productivity compared with a monolith catalyst with empty flow channels or the combination of inert monolith and bead catalyst. The monolith reactor had its highest productivity at relatively low liquid empty pipe velocities at 0.02-0.03 m/sec. The sphere-packed monolith reactor is promising because of its high productivity but needs further optimization in terms of bed configuration and associated pressure drop.