Rhabdomyoma is a rare tumor in the posterior mediastinum. We present a case of adult rhabdomyoma that occurred multifocally in the head, neck and mediastinum. There have been as few as four previous reports on rhabdomyoma in the posterior mediastinum. An 80-year-old white man was admitted to the Division of Pulmonary Diseases because of dyspnea, hemoptysis and fatigue. Physical examination revealed a tumor in the left submandibular area. Computed tomography (CT) of the head and neck showed a mass which caused a marked prominence of the left posterolateral wall of the pharynx. Chest CT revealed a contrast-enhancing tumor. The mass was 20 x 19 x 55 mm in size and was in contact with the lateral wall of the esophagus. Histological examination showed that the tumor was composed of cells typical of adult rhabdomyoma. The patient has been followed in our outpatient clinic for more than the last 7 years. To our knowledge, this is the fifth case of adult mediastinal rhabdomyoma. We believe that rhabdomyoma is a rare tumor which should be considered in a differential diagnosis of tumors detected in the posterior mediastinum.