AbstractA brief review is given of recent positron studies of metal and semiconductor nanocrystals. The prospects offered by positron annihilation as a sensitive method to access nanocrystal (NC) properties are described and compared with other experimental methods. The tunability of the electronic structure of nanocrystals underlies their great potential for application in many areas. Owing to their large surface‐to‐volume ratio, the surfaces and interfaces of NCs play a crucial role in determining their properties. Here we focus on positron 2D angular correlation of annihilation radiation (2D‐ACAR) and (two‐detector) Doppler studies for investigating surfaces and electronic properties of CdSe NCs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)