Hydrocarbon solvent-assisted processes are thought to be effective FOR technologies for heavy oil and bitumen production. In order to describe those processes quantitatively, the diffusivity of hydrocarbon solvent in oil sands is a crucial required parameter. Computer-assisted tomography (CAT), as a nonintrusive method, is a useful tool to obtain the physical properties of cores (density, porosity, heterogeneities) and the fluids within the cores (saturation or concentration profiles). However, the concentration profiles obtained from diffusion experiments of solvent in oil sands were fluctuating and could not be used to evaluate the diffusivity. In order to solve the problem, during the data processing of CAT scanning, porosity heterogeneity of porous media and volume changes on mixing are considered to improve the accuracy of concentration profiles dramatically. Subsequently, the diffusivity of hydrocarbon solvent in heavy-oil saturated sands is determined based on an updated mathematical model, which considers porosity heterogeneity of porous media in the major diffusion direction and volume changes on mixing. Thus, the diffusivity as a function of concentration and porosity is evaluated precisely and the impact of porosity heterogeneity of porous media on diffusivity determination of hydrocarbon solvent in heavy-oil saturated sands is investigated.