Diffusion of implanted (57)Co in ZnO has been determined in the temperature range 660-950 degrees C using the modified radiotracer technique. The diffusion was found to follow the Arrhenius type relation with an activation enthalpy of (2.9 +/- 0.3) eV and a pre-exponential factor of 3 x 10(-4) m(2)/s. Supported by diffusion data and conclusions provided in the literature, it is proposed that cobalt diffuses substitutionally in ZnO. (C) 2009 Elsevier B.V. All rights reserved.