AbstractThe tracer diffusion of deuterium and tritium in the β‐phase of PdHn has been measured by means of special techniques, the time lag method with mass spectrometer or counter tube as detector, and the decay function of isotope exchange. It has been found that D atoms as tracer in β‐PdHn, i.e. surrounded by H atoms, reveal a smaller mobility than in PdDn, where they are surrounded by their own species. T atoms in the β‐phase of PdHn showed about the same mobility as can be estimated — from results of α‐phase measurements ‐for PdTn.An explanation of this unexpected bevavior can be given by the assumption of displacement jumps as a particular type of correlation effect: by this the mobility of the tracer atoms becomes dependent on the mobility of the surrounding isotope species in the lattice.