Quasi-elastic neutron scattering (QENS) has been used to study water adsorbed at different concentrations in BaX zeolite. It is found that, the lower the water content, the higher the temperature which is required to reach adsorption equilibrium. For a loading of 15 molecules per supercage, an evolution of the QENS intensity with time is observed at 440 K which suggests that the sample was not in equilibrium; for a loading of 10 molecules per supercage, this happens at 520 K. Even at the highest studied temperature, 520 K, the diffusion coefficient of water in the equilibrated samples is lower than 10–12 m2 s–1. This is much lower than in NaCaA zeolites, manifesting the very large interaction between water and the Ba cations.