Diffusion in both the Pd‐Sn and Cu‐Sn systems has been investigated using differential scanning calorimetry. Averaged interdiffusion coefficients for the PdSn4, PdSn2 and Cu3Sn intermetallics have been calculated, where equilibrium concentrations in the diffusion couples are assumed. There is an obvious hierarchy within the Pd‐Sn system where diffusion is fastest in the most Sn‐rich intermetallic. Comparisons within each system, including consideration of the solute diffusion coefficients in pure Sn, provide evidence that in the most Sn rich phase (e.g. PdSn4) the interstitial diffusion of metal atoms is the dominant reaction mechanism. In contrast, the diffusion coefficient for the Cu‐rich phase Cu3Sn was found to be five orders of magnitude smaller than the solute diffusion coefficient for Cu in pure Sn.