The liquid distribution on the surface of structured packing, the holdup and the relative interfacial area are investigated using X-ray computed tomography (CT). Packed columns of two different inner diameters 100 mm and 200 mm are used and the fluid dynamics for MellapakTM of two different specific geometric areas are explored. Three-dimensional information is obtained by means of a helical scan. Despite deviations in the holdup profiles in detail, there is a good agreement between the average holdup and average relative interfacial area of Mellapak 500.Y measured in the two column diameters. Therefore, the 100 mm data of Mellapak 500.Y and the 200 mm data of Mellapak 250.Y are generally valid, and information is transferrable to larger column diameters. Relative interfacial area does not scale according to the liquid line load. Geometric features of the packings affect the flow morphology significantly, and in such a way that geometric similarity cannot be claimed for the two packings.