Anisotropic domain tilting of GaN films prepared by hydride vapor phase epitaxy (HVPE) on GaN/sapphire (0 0 0 1) substrate employing lateral epitaxial overgrowth (LEO) method has been investigated using high-resolution X-ray diffraction. Anisotropic domain tilting resulted in anisotropic broadening of GaN (0 0 0 2) Bragg peak and anisotropicity was fitted using a model based on anisotropic mosaic spreading. Anisotropicity of domain tilting, which was thought to be induced by stress gradient in the transition area between prepatterned SiO2 stripes and window region, relaxed with an increasing film thickness, but was still observed to exist up to a film thickness of 40 mu m.