Proton diffusion in NaHZr(PO4)(2)-5H(2)O and Na2Zr(PO4)(2)-3H(2)O phases was examined by studying the kinetics of hydrogen-sodium ion exchange. Three regions characterized by an almost linear dependence of the apparent diffusion coefficients of the hydrogen ion on the pH values were obtained at pH < 7, 7 < pH < 9 and 9 < pH < 11. The phenomenon was explained by different mechanisms of defect formation in the pH ranges investigated. The distribution of the proton defect concentration in the grains was estimated for different pH values, The influence of the anion nature in the contacting solutions on the diffusion coefficients was also discussed. The rate of ion exchange increases in the series: I- < Br- < Cl-, ClO4-