An approach to synthesize the electrophilic fluorinating agent no-carrier-added (n.c.a.) [ 18F]perchloryl fluoride ([ 18F]FClO 3) in superacidic media in the presence of KClO 4 or anhydrous perchloric acid starting from [ 18F]fluoride was demonstrated in this study. However, the radiochemical yields were low (1–6%) and poorly reproducible. Fluorosulphonic acid proved to be an essential intermediate as revealed by non-radioactive experiments. A key problem in the preparation of [ 18F]FClO 3 is the assumed kinetic inhibition due to the unfavourable stoichiometric ratio of the ClO 4 moiety to [ 18F]HSO 3F.