Fluorescence recovery after photobleaching (FRAP) experiments have been performed on a fluorescent dextran/poly(vinylpyrrolidone) (PVP) mixture in water. The experiments were made at several total Polymer concentrations C(T), from dilute to semidilute solution (0.1-10C*) in the homogeneous and disordered state. The composition of the "visible" polymer fluorescent dextran in the mixture was around 0.5 % in the semidilute regime. The dynamics of such a system as revealed by FRAP exhibit one relaxation mode identified as a self-diffusion coefficient. This mode has been compared to the extracted D(S) value from the two relaxation modes (cooperative and interdiffusive) obtained using dynamic light scattering (DLS; Macromolecules 1993, 26, 2592). As expected in both techniques, the measured (FRAP) and the extracted (DLS) D(S) decrease with the concentration. Comparison between the results shows that in the semidilute range of concentration the agreement is reasonable between both D(S). As the concentration decreases, the agreement becomes less and less satisfactory. This result confirms that the extrapolation to infinite dilution of D(S) (deduced from DLS) is not valid and shows the importance of the hydrodynamic interactions in the dilute ternary systems.