A submucosal injection of iodized oil (Lipiodol) was administered to patients with esophageal cancer and computed tomography scanning was performed. Infiltration to the surrounding organs, especially the aorta, vertebra, trachea, bronchi, heart, and lymph nodes was examined and the results compared with those from plain computed tomography. Compared with plain computed tomography findings, invasion to the submucosa, adventitia, and surrounding organs was much more clearly demonstrated. This method accurately delineated the oral side of mucosal lesions, which could be useful in establishing a plan for radiotherapy.