The two-phase flow distribution inside catalytic reactors operating under trickle-flow conditions was qualitatively studied. Three techniques were developed and applied to optimize the two-phase flow distribution through the catalyst bed. First, a computational fluid dynamic (CFD) tool was used to assist in the design of the inlet gas liquid distributor. Second, the corresponding flow inside a catalyst bed, in terms of liquid flow rate and liquid retention, was measured with the two other experimental techniques: a collecting device and a gamma-ray tomography system. These three techniques complement one another; their combined use is of value in the design and testing of reactor inlet distributors.