Hydrogen has been proposed as one of the contributors to the native n-type doping in as-grown Zinc Oxide and can also be used as an active (intentional) n-type dopant. In this work we have employed Secondary Ion Mass Spectrometry (SIMS) to study deuterium diffusion profiles in single crystalline ZnO. The samples used are hydrothermally grown, high-resistive (10 kΩ cm) monocrystalline ZnO implanted with deuterium to a dose of 1×1015 cm−2 yielding a peak concentration of approximately 5 × 1018 cm−3 at a depth of 2.2 µm. Diffusion profiles have been studied after 30 minutes isochronal heat treatments from 100ºC up to 400ºC in steps of 50ºC. The observed redistribution can be explained by employing a diffusion model which includes trapping of 2H by Li-impurities and an activation energy of 0.85 eV is extracted for the diffusion of 2H.