We present the results of sapphire/GaN substrate patterning on GaN film quality and on LED performance. MOVPE was used to grow GaN films on c‐plane sapphire. The films were then patterned with hexagonal holes with various diameters. When regrown with GaN, voids were formed in the sapphire/GaN interface. The void shape could be controlled from nearly vertical to inclined by changing the pattern dimensions. Patterning resulted also in reduced dislocation density of the overgrown GaN film. X‐ray diffraction and transmission electron microscopy results showed that the reduction is due to bending of edge‐type dislocations during the regrowth of the patterned substrate. Standard LEDs were grown on reference and patterned substrates and processed into chips. When grown on a patterned substrate LED chips showed approximately 10% increase in light output when compared to ones grown on a reference sample. The increase was attributed to improved light extraction. More improvement can be expected by optimizing the pattern geometry and the void shape. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)