Using a particle made of linear polystyrene (PS) chains as a core, we further poly merized a crosslinked PS shell on it in water to form a spherical core-shell particle (-100 nm). Such a particle swells in toluene or tetrahydrofuran (THF). The swelling enables entangled linear PS chains inside the core to gradually diffuse out through the porous shell. Using a combination of static and dynamic laser light scattering, we have examined effects of the shell thickness and cross-linking density (pore size) on the diffusion by following the change of the scattering intensity (i.e., the average molar mass of the core-shell particles). The diffusion exhibits three stages reflecting the concentration change inside the core, or more precisely, the relative change of the correlation length inside the core to the average pore size (d(pore)) in the shell, i.e., (1), < d(pore), (2) R-g > xi c, similar to d(pore), and (3) xi(c) similar to R-g >> d(pore), where R-g is the average radius of gyration of linear PS chains inside the core. It, is interesting to find that in the first stage the diffusion of the chains through the porous shell is even faster than their translational diffusion in a dilute solution.