In this work, we implemented the gamma-ray computed tomography (CT) technique to evaluate the new mechanistic scale-up methodology of gas-solid spouted beds by locally measuring the time-averaged cross-sectional distribution of solids and gas holdups, as well as their radial profiles along the bed height. The new scale-up methodology of geometrically similar beds is based on maintaining a similar radial profile of the gas holdup at a height within the bed, to achieve local and global similarity in dimensionless hydrodynamic parameters since the gas dynamic dictates the hydrodynamics of the gas-solid spouted bed. Two sizes of spouted beds (with diameters of 0.076 m and 0.152 m) were used with conditions that provided close magnitudes and trends of radial profiles of gas holdup; and with conditions that provide mismatches in magnitudes of the gas holdup radial profiles. The results clearly show the validity of the new method for scale-up, where the solids and gas holdup cross-sectional distributions and profiles are close to each other at all the heights and in the three regions (spout, annulus and fountain) of spouted beds, when the radial profiles of the gas holdup are close at one height between the two studied beds. In addition, the CT results clearly identified three regions mentioned above (spout, annulus, and fountain regions). In the spout region, the solids holdup increases along the spout height. When the radial profiles of gas holdups are different in two spouted beds, the differences are noticeable in local solids and gas holdups in all the heights, which further endorse the new mechanistic scale-up methodology.