Pulsed-field gradient NMR spectroscopy was used to study the diffusion of three different poly(propyleneimine) dendrimers with hydrophilic triethylenoxy methyl ether terminal groups (generations 2, 4, and 5) in poly(vinyl alcohol) aqueous solutions and gels. The effects of the diffusant size, polymer concentration (from 0 to 0.26 g/mL), and temperature on the self-diffusion coefficients have been studied, and the model of Petit et al. [Macromolecules 1996, 29, 6031] was used to fit the experimental data. The Stokes-Einstein hard-sphere radii were also calculated in the zero concentration limit and were compared with those of the linear poly(ethylene glycol)s under the same conditions. The proton NMR relaxation times (T-1 and T-2) were measured to study the mobility of the dendrimer core part and terminal group as a function of the dendrimer size.