The positron-emitting nuclide fluorine-18 is of great importance to modern nuclear medicine with the increasing clinic demands of positron emission tomography (PET) and R&D of PET radiopharmaceuticals worldwide. Fluorine-18 can be introduced into a target molecule to prepare the corresponding 18F-labeled radiopharmaceuticals through direct and indirect radiofluorinations. However

it is not suitable for the preparation of biomacromolecular-oriented radiopharmaceuticals such as peptides and protein using the direct labeling methods because of the lack of reaction selectivity. Thus

it is necessary to choose an appropriate 18F-labeled intermediate for the indirect labeling methods. According to the classification of precursors displaced by 18F

this paper briefly introduces two species of 18F-labeled intermediates originated from aliphatic and aromatic displacements and their syntheses and applications in PET radiopharmaceutical domain.