This mini-review covers the issues concerning the application of microfluidics towards radiolabelling with short-lived isotopes used for PET (positron emission tomography), and surveys the literature in this area. The application of microfluidic reactors to radiolabelling reactions is currently receiving a great deal of interest because of the potential advantages they have over conventional labelling systems. The volume and variety of radiolabelling reactions for PET is expected to grow markedly over the coming years due to increased demands for PET scanning. High demands and expectations for radiolabelled compounds will have to be met by exploiting new types of chemistry and technologies, such as microfluidics, to improve the production and development of PET tracers. (C) 2008 Society of Chemical Industry