Tin oxide nanostructures with controlled narrow particle size distribution were synthesized inside silica mesoporous templates. In this way, particle growth was blocked by physically corseting the tin compound inside the silica frameworks, the pore diameter of which determines the final tin oxide crystallite size distribution. Template structures were subsequently eliminated by chemical methods to collect the unsupported semiconductor nanoparticles. Thus obtained tin oxide nanopowders, with particle sizes in the range between 6 and 10 nm, were structurally, chemically, and electrically characterized. The results are compared with those obtained from the characterization of larger crystallite materials. (C) 2004 The Electrochemical Society.