The variations of equilibrium oxygen content with oxygen pressure and temperature were measured in copper doped double perovskite cobaltite PrBaCo2-xCuxO5+delta. The results of thermodynamic analysis show that oxygen pressure decrease and temperature increase both favor the appearance of oxygen vacancies in O2 structural positions. It is suggested that oxygen migration over O3 positions in double perovskite cobaltites occurs via mediation of O2 positions. Copper doping is shown to facilitate formation of oxygen vacancies in O2 positions, which is expected to be advantageous for enhanced oxygen ion transport. (C) 2015 Elsevier B.V. All rights reserved.