Hexagonal GaN pyramids have been fabricated by hot-wall metal organic chemical vapor deposition (hot-wall MOCVD) and the growth evolution has been studied. It was concluded that the pyramid growth can be divided into two regimes separated by the adsorption kinetics of the {11¯01} surfaces of the pyramids. In the adsorption regime, the pyramids grow simultaneously in the <11¯01> and [0001] directions. In the zero-adsorption regime the pyramids grow only in the [0001] direction. Thus the pyramid growth ceases when the (0001) facet growth has been terminated. Large arrays consisting of highly uniform pyramids with apex radii of 3nm or less were achieved in the zero-adsorption regime. The growth-regime type was concluded to have a large impact on the uniformity degradation of the pyramids, and their optical properties. The impacts of threading dislocations which enter the pyramid from underneath are also discussed.