Transplantation of cells into damaged tissue has tremendous therapeutic potential in a number of disorders, such as Parkinson's disease and myocardial infarction. Positron emission tomography (PET) and single photon emission tomography (SPECT) are highly sensitive imaging modalities, which can detect and track these cellular implants through a number of mechanisms. The stable transfection of cells with a reporter gene, which can be visualized using a radioactive PET or SPECT reporter probe, allows the repeated visualization of the migration and function of cells. These imaging techniques can be used to assess cell trafficking with methods that are easily translatable to humans. This review describes several reporter genes for PET and SPECT, and compares them against other techniques and imaging modalities.