Thymoma is the most common cancer of the anterior mediastinal compartment. It represents the 20% of all mediastinal tumors in adult and about 50% of anterior mediastinal cancer. Thymoma typically occurs in people with age of 40-60 years. Recognition of thymoma is very important, because a complete resection of the tumor gives an excellent prognosis. Diagnostic imaging plays a key role in the study of mediastinal diseases and thymoma. Multidetector computed tomography (MDCT) might allow a characterization of the lesion and proper treatment planning. We report the case of a man with cholelithiasis that during preoperative examinations reported a large asymptomatic thymoma.