Abstract: With the development of three dimensional conformal radiotherapy and intensity modulated radiotherapy, radiotherapy becomes an important treatment for esophageal cancer. Accurate staging and target volume delineation are prerequisites for a successful treatment of esophageal cancer with radiotherapy. Conventional cross-sectional images are helpful for guiding radiotherapy plans, assessing treatment response and detecting recurrence. But there are still many limitations for anatomic information alone. PET/CT is an imaging fusion modality which may overcome some limitations of conventional cross-sectional modalities. It plays an important role in the diagnosis and treatment of esophageal cancer. This review evaluates the applications of 18F-FDG PET/CT in the initial staging before radiotherapy, its target volume definition, treatment response and the prognosis of esophageal cancer.