(123)I-labeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane ((123)I-FP-CIT) was approved for clinical use in 2011 by the Food and Drug Administration. (123)I-FP-CIT is a radioligand for brain dopamine transporter (DAT) imaging that is useful for the differential diagnosis of Parkinson disease (PD) and other diseases that mimic PD. The sensitivity and specificity of (123)I-FP-CIT SPECT for PD diagnosis are more than 90% and equivalent to those of other DAT SPECT methods. In the near future, the clinical indications of DAT imaging are expected to be broadened; for example, including treatment response assessment, disease progression monitoring, and early diagnosis of premotor PD in each individual patient.