Correlations between positron annihilation lifetime spectroscopy (PALS) measurement and diffusivities in polymer solutions were established, with the hell) of the Simha-Someynsky (SS) equation-of-state (EOS) and the free-volume theory. Mean hole volume probed by PALS was employed to predict the free volume available for solvent transport and solvent diffusion coefficient. The predictions of infinite dilution diffusion coefficients of four organic solvents in two common polymers were generally consistent with the published experimental values. Hole size distribution from PALS results was also investigated to prove the reliability of this new approach.