Diffusion of oxygen ions in yttria-stabilized zirconia was studied using constant-volume molecular dynamics simulations for temperatures ranging from 1000 K to 2000 K and for varied compositions between 4 and 12 mol% Y2O3. Non-monotonic dependence of diffusion coefficients on yttria content was observed with a maximum at 5-7 mol%. With increasing temperature the position of diffusion maximum was drifting towards higher Y2O3 content The highest oxygen diffusion coefficients were obtained for Y2O3 concentrations close to the limit of cubic phase stability region. Diffusion activation energies increased monotonically with increasing concentration of the dopant. (C) 2014 Elsevier B.V. All rights reserved.