When applied to a radiosynthesis, a microscale approach can help to save precursor and improve yields. Thus, a 5-10 mu L. microscale method based on a concentration procedure was developed and applied to the radiosynthesis of [F-18]FET and [F-18]fallypride. In spite of using an amount of precursor ca. 100 times smaller, radiochemical yields were comparable or even higher than those reported in literature. Because of the very low reaction volumes, the possible effects of concentrated dose of activity and carrier fluoride were also investigated.