Theself-diffusionofREisotopesinporouscationexchangerswithvariousparticlesizeandinseveralMR-typeresinsnEDTAsolutionsofrareearthswasstudied.TheintraparticleeffectivediffusivitiesDeofCe,TbandYbweremeasuredbyisotopicionexchange,DewasaffectedbytheconcentrationofthebulksolutionandwasseparatedintoasolidphasediffusivityDgandamacroporediffusivityDpusingKataoka′sdidisperseporemodel.Itshowsthatthemodelcanbeappliedtoexpressthekineticprocess;DemuchlargerthanDeandDgisnearlyequaltoDe.Solidphaseresistanceisamajorcomponentofresistancetotheexchangeforporousresins.