During cheese ripening, bacteria grow as immobilized colonies, metabolizing substrates present in the matrix and generating products triggered by enzymatic reactions. Substrates have to diffuse through the matrix to reach the colonies. Then, metabolites may also diffuse from the colonies into the matrix. Local limitation rates of diffusion, either in the matrix or in the colonies, can be responsible for modulation of the metabolic activities of bacteria and thus for the final quality of the product. Diffusion phenomena depend both on cheese microstructure and on physicochemical characteristics of the solutes (charge, size, shape, etc.). Floury et al. (2012) recently showed the great potentiality of the Fluorescence Recovery after Photobleaching (FRAP) technique to study the diffusion of fluorescent solutes in cheeses. The determination of the relationship between diffusion properties of substrates and metabolites (solutes) and the structure of the matrix is an important step to understand cheese ripening mechanisms. The main aim of this study was to investigate the diffusion coefficients of solutes (FITCdextrans and FITClabeled dairy proteins) of different sizes (radius 1.4 to 27 nm), and shapes (flexible and rigid) in a model cheese (obtained from ultrafiltered milk) with controlled microstructure and texture. Structural parameters of the proteinic network, such as fractal dimension, pore size, porosity and tortuosity, were determined by a combination of macroscopic (rheology, permeability) and microscopic (CLSM, TEM) techniques. These studies are under way in an effort to elucidate the influence of the structure of the matrix on the diffusion of solutes in model cheese matrices. A better understanding of the influence of matrix microstructure on the mobility of these solutes should allow a more generic view of cheeseripening kinetics for future innovations.