Colloidal SnO2 nanocrystals are prepared via a solvothermal method using oleic acid as a stabilizing agent. Preferred orientation growth along [001] direction of colloidal SnO2 nanocrystals is observed, thereby pure SnO2 nanoparticles with quasi-sphere shape being converted to nanorods due to Gd3+ ions doping. In addition, with increasing Gd3+ doping concentration, the size of SnO2 nanorods decreases. The decrease in size and the change in the shape are ascribed to the increase in the growth rate along [001] direction due to the cationic doping with a surface charge modification. Our results demonstrate a simple method to tune the size and shape of SnO2 nanocrystals through cationic doping with Gd3+ ions. (c) 2013 Elsevier B.V. All rights reserved.