Abstract. We have studied X-ray absorption fine structures (XAFS) of Pt nanoparticles (PtNPs) which were deposited on silicon nanowires (SiNWs). SiNWs were fabricated via an electroless chemical etching method and served as the template for the immobilization of PtNPs. PtNPs electrolessly reduced from their ionic solution by HF-treated SiNWs were found to deposit on the tips of the SiNWs. The electronic structures of Pt were studied using X-ray absorption near-edge structures (XANES) at Pt L_3,2-edge. For comparison, we also examined the Pt L_3,2-edge and the Au L₃-edge XANES of Pt-Au bimetallic nanoparticles co-deposited on SiNWs. We found that the PtNPs showed slightly increased whiteline intensity compared to that of Pt foil. When Au was deposited together with Pt, the resonance peaks of the NPs were slightly, but systematically shifted due to the formation of Pt-Au alloy.