Notwithstanding the importance of materials, microstructure also plays a significant role in performances of solid oxide cells. X-ray nanotomography with a voxel size of 25 nm was used to image the microstructure of CGO-LSCF composite oxygen electrode obtained by electrostatic spray deposition (ESD). The stack of data was used to create a 3D model. Two volumes were selected from the 3D model and microstructural parameters like porosity, surface area, percolation path and tortuosity factor were computed to quantify the microstructure. The influence of the applied threshold values on the parameters was investigated. Comparison of these parameters with previously reported data has shown significant differences. The porosity of CGO-LSCF oxygen electrode varied from 67 to 87 vol.%. Such a high porosity level makes this ESD microstructure unique. The microstructural parameters were used to determine the electrode polarization by Adler-Lane-Steele model. Modeled polarization resistance was in an agreement with experimental data. (C) 2015 Elsevier Ltd. All rights reserved.