This article reviews the use of x-ray computed tomography (XRCT) to investigate the structure and properties of cellular solids. In the first section, the possibilities offered by XRCT are presented. Examples of tomographic images are shown for the three classes of material (polymers, metals, and ceramics). Different characterizations of cellular solids performed thanks to XRCT images are shown: calculation of morphological parameters, in situ and ex situ mechanical tests, and use of the tomographic images to perform finite element (FE) modeling. The second part of the paper presents the existing methods to create the meshes from tomographic images and highlights some interesting results from the FE simulations.