Positron emission tomography (PET) is a powerful and rapidly developing area of molecular imaging that is used to study and visualize human physiology by the detection of positron-emitting radiopharmaceuticals. Information about metabolism, receptor/enzyme function, and biochemical mechanisms in living tissue can be obtained directly from PET experiments. In particular, the interest in 18F-labeled proteins remains high for both diagnoses and therapy monitoring purposes. The development of labeling strategies for the synthesis of new 18F labeled protein is, however, not trivial. 18F-containing prosthetic groups are often required for protein labeling to obtain high yield under mild labeling conditions and keep the bioactive character of the proteins. This review highlights key aspects of protein 18F-labeling method and discussed representative examples including 18F-labeled human serum albumin, 18F-labeled Annexin V, 18F-labeled HER2 affibody, and 18F-labeled low density lipoprotein.