Digital quantification of a two-dimensional structure was applied to a GDC(Gd2O3-doped CeO2)/LSM(La0.85Sr0.15MnO3) composite cathode employed for solid oxide fuel cells. With the aid of high-resolution imaging capability based on secondary and backscattered electron images, two-dimensional electron micrographs were converted to digital binary files using an image processing tool combined with the line intercept method. Statistical analysis combined with a metallurgical tool was employed to determine microstructural factors, i.e., volume fraction, size distribution, and interconnectivity. The current work reports the quantification of the two-dimensional structural images of GDC/LSM composites applicable to solid oxide fuel cells, with the aim of obtaining the volume fraction, size distribution, and interconnectivity as functions of composite composition. The volume fractions of the solid constituent phases exhibit compositional dependence in cathodes; however, LSM interconnectivity increases gradually as a function of LSM composition, whereas that of GDC decreases significantly at 50 wt% LSM.