In cheese technology, the diffusion phenomena are crucial during ripening. The technique of Fluorescence Recovery After Photobleaching was applied for the first time on real cheese, in order to investigate the relationships between molecular diffusion and the cheese composition and/or its microstructure. Measured effective diffusion coefficients in soft and hard cheese of a group of dextrans (10–500 kDa) were found to be in the same order of magnitude with values observed when using a comparable non-fat model cheese ( 0.1–20 lm2 s 1). Diffusion of the dextrans was mainly dependent on the fraction of ‘‘free’’ aqueous phase present in the cheese, closely which is linked to cheese-making technology and ripening stage. Diffusion coefficients were modeled by a power law relationship as a function of dextran molecular weight, which allowed some study of the cheese microstructure. A tighter protein network will require some deformation of those flexible macromolecules with a higher molecular weight (>250 kDa), in order to diffuse through the pores of such cheese structures.