A- and B-site cation diffusion in the La2NiO4+delta system was investigated by, respectively, La2NiO4+delta-Nd2NiO4+delta and La2NiO4+delta-La2CuO4+delta inter-diffusion couples, annealed 100-600 h in ambient air at 950-1300 degrees C. Concentration profiles of the inter-diffusing cations were obtained by means of Electron Probe Micro Analysis (EPMA) from cross-sections. These profiles were fitted to the solution of Fick's second law for constant source and to Whipple-Le Claire's equation from which bulk and grain boundary diffusion coefficients, respectively, were derived. The diffusivity of A- and B-site cations in the grain interiors (bulk) Are essentially comparable, while grain boundary diffusion of the B-site cations is enhanced, around 5 orders of magnitude within the investigated temperature range. Element mapping of the cross-sections of La2NiO4+delta-La2CuO4+delta couples visualises the enhanced grain boundary diffusion of B-site cations. The activation energies are 275 +/- 12 kJ/mol for A-site bulk diffusion, and 450 +/- 20 and 125 +/- 24 kJ/mol for B-site bulk and grain boundary diffusion, respectively. (c) 2012 Elsevier B.V. All rights reserved.