X-ray diffraction (XRD) measurements were carried out in order to investigate the structure of bismuth nanoparticles. The x-ray diffraction profile of the as-deposited sample has broad peaks originated from Bi nanoparticles. The peaks become sharp and the intensities increase with annealing at 300°C. A halo pattern was extracted from analysis of background in the as-deposited samples. The existence of the halo pattern implies that the as-deposited nanoparticles contain of the amorphous phase. [DOI: 10.1380/ejssnt.2007.110]