This review focuses on the clinical use of PET in esophageal cancer. For initial staging of esophageal cancer, PET is better than chest CT and is complementary to endoscopic ultrasound. Due to its good results for detecting distant metastasis, PET evades unnecessary curative surgery. Also, PET findings are associated with prognosis in esophageal cancer. PET seems to be useful for detecting recurrence and restaging in esophageal cancer. For therapy response assessment, PET is effective after chemotherapy or radiation therapy. PET is useful to predict pathological response after neoadjuvant therapy in esophageal cancer, which is better than chest CT and endoscopic ultrasound. For radiation therapy planning, PET may be helpful, but requires further investigations.