Mathematical models describing drying processes are required for engineering design and optimisation purposes. In the literature, diffusional models, with different levels of complexity, are developed for the description of air drying, particularly, of fruits and vegetables. In this review different models are proposed for regular shaped bodies (spheres, parallelepipeds and cylinders), where different phenomena are taken into account (isotropic or non-isotropic behaviour of the solid regarding mass transfer, sample shrinkage, heat transfer and sample temperature variation during the drying process, the dependence of the effective diffusivity coefficient on moisture and temperature, etc.). The methodologies used to solve the model equations, to identify model parameters and to validate the proposed model are discussed in terms of simplicity, accuracy of moisture prediction and applicability to various food materials.