SnO2 nanobelts and nanocrystals have been synthesized in large quantity using the thermal evaporation and oxidation method via careful control of experimental parameters. The products were characterized with scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, and ultraviolet absorption spectroscopy. The as-synthesized SnO2 nanobelts primarily consist of tetragonal rutile structure and orthorhombic phases, whereas the composition of the SnO2 nanocrystals is a relative pure rutile structure. Detailed microstructure characterization reveals that stacking faults and a layered structure exist in the nanobelts and a twin structure was frequently observed in the nanocrystals. The ultraviolet absorption spectra of these two nanostructures were measured. Based on the above microstructural and optical results, the possible growth mechanism, and the structure properties relationship were discussed for the nanobelts and nanocrystals. (C) 2008 Elsevier B.V. All rights reserved.