The vesicular acetylcholine transporter ligand (-)-(1-((2R,3R)-8-(2-[(18)F]fluoro-ethoxy)-3-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)piperidin-4-yl)(4-fluorophenyl)-methanone (18F -VAT) enables positron emission tomography PET quantification of cholinergic dysfunction in neurologic and psychiatric disorders. The gene discussed is SLC18A3; the disease is psychiatric disorder.