An asymptomatic 59-year-old female was admitted with an abnormal shadow on her chest radiography. Chest computed tomography (CT) revealed a mass measuring 20 mm in the anterior mediastinum. At the arterial phase on dynamic contrast-enhanced CT (dynamic CT), the pattern of "peripheral puddles", defined as discrete well-defined peripheral enhancing globles, was found in the mass. The tumor was completely resected via a median sternotomy, and was histopathologicaly diagnosed as hemangioma. In this case, dynamic CT was very useful for the preoperative diagnosis, and then the enhancement pattern of "peripheral puddles" on dynamic CT may be a conclusive finding for the diagnosis of mediastinal hemangiomas.