NMR measurements of proton rotating-frame relaxation times were made to deduce hydrogen diffusion parameters for crystalline and amorphous Zr 2PdH x. Enhanced proton mobility was observed in glassy a-Zr 2PdH 2.9 relative to diffusion behavior in any crystalline Zr 2PdH x sample. Both host crystal structure and proton site occupancy make significant contributions to the diffusion process where smaller activation energies correspond to jumps involving octahedral sites.