We report on the presence of optically active stacking faults on basal and prismatic planes in epitaxially laterally overgrown GaN (ELOG) on {11 2- 2} facets. The structure of the faults has been analyzed using diffraction contrast electron microscopy. We show that stacking faults on {11 2- 0} prismatic planes involve a lattice displacement of 1 2 〈1 1- 01〉, parallel to the fault plane. They appear as jogs connecting basal-plane stacking faults, the latter with a lattice displacement of 1 6 〈20 2- 3〉. These faults are observed only in the laterally overgrown regions that grow on {11 2- 2} planes, which indicates that the stacking fault formation is closely related to the orientation of the growth surface. Possible formation mechanisms of these faults are discussed. Direct correlation between TEM and cathodoluminescence shows that these prismatic-plane and basal-plane stacking faults are optically active with light emission at 3.30 and 3.41 eV, respectively. © 2006 American Institute of Physics.