Ab initio DFT simulations of Zn and O atoms and O-2 molecules adsorption on polar 2H-ZnO(0001) and 2H-ZnO(0001) surfaces elucidated the principal processes, important for growth of zinc oxide from the vapour. It was shown that a zinc atom is adsorbed at both ZnO surfaces without any energy barrier but with ultimately different adsorption energies: 0.34 eV for the metallic and 3.37 for the non-metallic surface. Oxygen atoms are attached very strongly at both polar surfaces, with energies equal to 5.47 eV and 2.47 eV. The difference between both polar surfaces is the largest for adsorption of molecular oxygen, the O-2 molecule is adsorbed on the Zn-face with the energy 2.45 eV while it is not adsorbed at the oxygen face of zinc oxide. (c) 2013 Elsevier B.V. All rights reserved.