An apparatus for the preparation of 11 C methyl iodide comprises a first reaction vessel wherein the internal surface is coated with a solution of lithium aluminium hydride, wherein the first reaction vessel has an internal diameter not greater than about 1.5mm. 11 C carbon dioxide is introduced into the first reaction vessel and reduced by the lithium aluminium hydride to give a reduction product； and reacting the reduction product with hydriodic acid.
