Fatty acid amide hydrolase (FAAH) is one of the main enzymes responsible for terminating the signaling of endocannabinoids, including anandamide. This paper is the first report of the synthesis, [123I]-labeling and in vitro and in vivo evaluation of anandamide analogues as potential metabolic trapping radioligands for in vivo evaluation of brain FAAH. N-(2-iodoethyl)linoleoylamide (2) and N-(2-iodoethyl)arachidonylamide (4) were synthesized with good yields (75% and 86%, respectively) in a two steps procedure starting from their respective acids. In vitro analyses, performed using recombinant rat FAAH and [3H]-anandamide, demonstrated interaction of 2 and 4 with FAAH (IC50 values of 5.78 microM and 3.14 microM, respectively). [123I]-2 and [123I]-4 were synthesized with radiochemical yields of 21% and 12%, respectively, and radiochemical purities were > 90%. Biodistribution studies in mice demonstrated brain uptake for both tracers (maximum values of 1.23%ID/g at 3 min pi for [123I]-2 and 0.58%ID/g at 10 min pi for [123I]-4). However, stability studies demonstrated the sensitivity of both tracers to dehalogenation.