A model has been constructed to determine the transport properties of porous media where the total tortuosity associated with the void space of a particular porous medium has independent contributions fi:om the structural features of the material over Various lengthscales. CCA fractal model structures have been used to represent the structural characteristics of real pellets over micro/mesoscopic (up to similar to 10 mu m) and macroscopic(>10 mu m) lengthscales that are probed by NMR experimental techniques sensitive to these lengthscales. NMR relaxometry and mercury porosimetry have been used to study the micro/mesoscopic scale and Magnetic Resonance Imaging (MRI) has been used to study the macroscopic scale. In combination with simulations of molecular diffusion using a finite difference algorithm, a model structure consisting of a hierarchical combination of micro/mesoscopic and macroscopic lengthscale models has been shown to give excellent predictions of the total tortuosity of real pellets determined by MRI methods.