In an effort to further understand the effects of molecular size and shape of macromolecular diffusants on the diffusion in hydrophilic polymer solutions and gels, hyperbranched polyglycidols have been synthesized as hydrophilic diffusants and characterized. Four of these hyperbranched polymers were selected for the study of self-diffusion by pulsed-field gradient NMR spectroscopy in poly(vinyl alcohol)-water systems. The effects of the molecular weight, size, and shape of the diffusant, polymer concentration, and temperature have been studied. For diffusants of similar molecular weight and without specific interactions, the activation energy decreases from the dendrimers to hyperbranched polymers and then to linear polymers. The results indicate that the molecular shape, and hence the molecular density distribution of the diffusants, is important in the diffusion process.