B diffusion in crystalline Ge is investigated under equilibrium and non-equilibrium conditions in a large temperature range (200–800 °C), in order to discriminate the role of self-interstitials (Is) and the energy barriers involved in the microscopic mechanism of B migration. To this aim, we copiously furnished Is by 200 or 300 keV H+ irradiation, and performed a direct comparison with B diffusion in thermal conditions at the same temperature (T). The diffused profiles of B were simulated assuming the kick-out model, and the extracted parameters (migration length, λ, and formation rate of mobile B, g) indicated that the B diffusion is always mediated by Is showing different features at low and high T regimes. For T lower than 600 °C the thermal generation of Is is negligible and the only barrier to g (measured to be ∼0.1 eV) is due to the Is migration and B mobile formation. At T higher than 600 °C, the thermal generation of I …