X-ray microtomography has been applied to characterize inhomogeneous microstracture and micro structure/property relationships in a cast Al-Zn-Mg alloy foam. 3-D distribution of Zn, Ca, Ti and H2 (i.e. pore) are visualized by capturing 3-D images just below and above the K-edge of Zn and then subtracting them from each other. It has been clarified that the distributions of alloying elements were inhomogeneous throughout the material. Brittle fracture of a cell wall appeared to be induced by the existence of Zn-rich intermetallic particles with segregated Ca. It has also been confirmed that coarse Ti-bearing particles, which are residual foaming agent added to alloy melts, remained intact during the deformation. Overall, the approach taken in this study has provided highly effective ways to characterize microstructure/properties relationships in such highly heterogeneous materials.