For CdSe nanoparticles it has been theoretically and experimentally shown that at low temperatures the photoluminescence is circularly polarized in accordance with a wurtzite structure and the corresponding allowed optical transitions. In the present Letter, we report on related investigations on CdSe/ZnS colloids in toluene solution. From time resolved photoluminescence anisotropy we conclude that also at room temperature the results are in good agreement with structure and related electronic states as determined from crystals at low temperature. (C) 2004 Elsevier B.V. All rights reserved.