with potent in vitro binding affinities for the cannabinoid subtype-2 (CB2) receptor were labeled with a positron-emitting radioactive nuclide 11C. Radioligands [11C]2, [11C]5, and their analogs [11C]3 and [11C]4 were synthesized by O-[11C]methylation of their corresponding phenol precursors with [11C]CH3I. [11C]2–5 had relatively high uptakes (>1.2% injected dose/g tissue) in mouse brains.