2,5-dimethoxy-N-benzylphenethylamines (NBOMes) are very potent 5-HT2AR agonists. Illicit use of these psychedelic compounds has emerged in recent years, and several fatalities have been linked to their recreational use. In its [11C]-labelled form, one NBOMe (25B-NBOMe) was recently developed as a PET-ligand for clinical investigations of the 5HT2AR ([11C]Cimbi-36). Herein, we have identified the phase I and phase II metabolites of 25B-NBOMe in pigs as well as in humans. We find that the primary route of metabolism is 5'-demethylation, followed by conjugation to glucuronic acid. [11C]-labelling of 25B-NBOMe in three different positions followed by in vivo evaluation in pigs and in humans corroborated these findings.