In order to evaluate the neurobiological mechanism causing the psychogenic effects of N-methyl-2,5-dimethoxy-4-methylamphetamine (MDOM), the11C labelled analogue was prepared for application in in vivo PET studies by the reaction of 2,5-dimethoxy-4-methylamphetamine (DOM) with [11C]CH3I. The radiochemical yield was determined in dependence on time, temperature, solvent and amount of substrate. The best conditions for fast labelling reactions with11C on a preparative scale were found to be a reaction time of 10 miutes at 110°C using 1 mg DOM in acetonitrile thus obtaining radiochemical yields of 80% (based on produced [11C]CH3I).