We have prepared GaN-core/Pt-shell composite nanowires via a two-step process. With the crystalline Pt shell layer being deposited with a deposition rate of about 4.5 nm/min, it was agglomerated to become cluster-like structures by the subsequent thermal annealing. The shell layers corresponded mainly to a cubic Pt phase regardless of annealing, whereas PtOx phases were additionally observed. From Gaussian deconvolution studies, the photoluminescence (PL) spectra were divided into three Gaussian functions, which were centered in the ultraviolet (UV), green, and red region, respectively. The overall PL intensity was increased by increasing the annealing temperature. We have discussed the associated PL mechanisms. (C) 2009 Elsevier B.V. All rights reserved.