In the Held of gas-solid fluidization, bubbles, and all features regarding them, have a very great importance, as they significantly affect the process performance. Numerous experimental studies on bubbles, and their formation, evolution, and properties, have been performed in the past. These investigations appear particularly difficult, due to the nature of these systems, since the gas phase is distributed in both the bubble and the emulsion phase. Several experimental approaches have been developed to tackle this study. Among these, the Digital Image Analysis Technique purposely developed in Part I of the present work, based on the use of a video camera for monitoring the phenomenon coupled with image analysis has been found viable and effective. Moreover, the bubbles behaviour and characteristics have been described by means of a variety of mathematical models. In recent years, in particular, computational fluid dynamics (CFD) tools have been found to be very effective in providing a powerful framework through which these models can be implemented and numerically solved. This paper combines both experimental and computational studies, presenting the comparison, performed by DIAT, between experimental data and relevant CFD Simulations. In particular, simulations have been performed by means of the ANSYS-CFX code. The comparison comprises the following quantities: bed expansion, bubble hold-up, size evolution, distribution, density, aspect ratio. and bubble velocimetry data. (C) 2008 Elsevier B.V. All rights reserved.