The crystal quality and light output power of GaN-based LEDs grown on nanoporous patterned sapphire substrate (NPSS) were investigated. NPSS was prepared using an anodized aluminum oxide (AAO) layer. It was found that the crystal quality of GaN-based LEDs grown on NPSS was better than that on micron-sized patterned sapphire substrate (MPSS) and conventional sapphire substrate. However, the light output power of GaN-based LEDs grown on NPSS was smaller than that on MPSS because the light extraction efficiency (LEE) of MPSS was much larger than that of NPSS.