Fluctuations of H2O molecules in the crystallized sample HfF4 center dot 3H(2)O have been studied in the temperature range 298-363 K by perturbed angular correlation (PAC) technique. In this crystal, apart from static components, time dependent relaxed component has been observed at these temperatures. The relaxation constants are found to increase with temperature up to 353 K following the Arrehenius equation and then decreases at 363 K where a chemical transformation in the sample has been observed. The time dependent relaxed component has been attributed to the fluctuation of H2O molecule in HfF4 center dot 3H(2)O. From the measured relaxation constants at different temperatures, activation energy for the H2O molecule has been found to be 0.15(1) eV. (C) 2010 Elsevier B.V. All rights reserved.