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Two nickel monocrystals of (111) and (100) orientation have been selected. The crystallographic influence on creep properties and on oxygen diffusion has been studied. For the diffusion analysis, an oxygen isotope ( 18 O) was used and investigated in NiO using nuclear reaction analysis. The oxide scale at 550°C is duplex. Moreover in creep, this microstructure presents periodic cracks. Two different mechanisms of creep are observed; i.e. interfaces sliding for NiO/Ni (111) and power law creep for NiO/Ni (100). Oxygen mobility is largely influenced by the application of stress and its level. The oxide layer integrity and the generated defects during creep are the main factors for the two crystallographic orientations. Hence, a synergetic effect was observed between the mechanisms of deformation in creep and the diffusion parameters with this simple metal oxide system. We also noticed an effect of the crystallographic orientation of nickel on the reactivity of the surface and on mechanical behaviour of the oxide layer.