Abstract: Iodine-124 (¹²⁴I) is an isotope for positron as well as unique chemical properties and convenient halflife of 4.2 days. Its modes of decay are 74.4% electron captureand 25.6% positron emission. Until recently, ¹²⁴I is not considered to be an attractive isotope for medical application owing to its complex radioactive decay scheme and the high-energy gamma rays. ¹²⁴I can be made by numerous nuclear reactions via a cyclotron. The most common starting material is ¹²⁴Te and ¹²⁴I that can decay to ¹²⁴Te. ¹²⁴I as sodium iodine form can be used to image the thyroid and corresponding tumor using positron emission tomography (PET) directly. The ¹²⁴I nuclide can be chemically bonded to a pharmaceutical to form a positron-emitting radiopharmaceutical. Radioiodination of ¹²⁴I can be efficiency attached to small molecular, peptide or antibody within radiochemistry labs. Nowadays, due to the increasing application of PET in medical oncology, pharmacokinetics and drug metabolism, ¹²⁴I-labeled radiopharmaceuticals are now becoming one of the most useful tools for PET imaging. ¹²⁴I-labeled monoclonal antibodies (mAbs) are being used for clinical immuno-PET. Among them, ¹²⁴I-cG250 accurately identifies clear-cell renal carcinoma attracting clinical attentions. Based on those progress, this review outlined the physical property, production and application of ¹²⁴I in PET molecular imaging.