Introduction:Mediastinum contains different vital structures that are located in the anterior and middle or posterior compartments. Various types of mediastinal masses or tumors can be seen in the mediastinum. Materials and Methods:This case series study was performed on 95 patients who had referred to Mashhad University of Medical Sciences between 1990 and 2010 were reviewed. The Inclusion criteria were as follows: Having primary mediastinal masses; Exact tissue pathology; Having received suitable treatment as well as having completed a 3-year follow-up after surgery; The major variables were age, sex, clinical symptoms, mass location, diagnostic procedures, imaging studies, tissue pathology, postoperative complications, mortality and a long-term survival. The patients were followed up for 3 years after the surgery. Results:Ninety-five patients enrolled in the study with M/F=51/44 and the mean age of 35.4+16.52 years. Moreover, anterior mediastinum was the compartment mostly involved in case of 66 patients with the lymphoma (n=39) as the most prevalent tumor of anterior mediastinum. Mediastinal cysts (n=10) in the middle part and neurogenic tumors (n=19) in the posterior mediastinum were the other prevalent tumors in the patients’ compartments. Transthoracic Needle Biopsy was used in the diagnosis of 37 cases. Furthermore, 43 patients underwent surgery alone, 7 cases underwent surgery followed by receiving adjuvant therapy and 45 cases received adjuvant therapy alone. Complications emerged in 15 cases and 9 patients expired before the completion of the 3-year follow-up. Three of the mortalities happened during the patients’ hospital treatment. Conclusions: In case of anterior mediastinum, pre-operation clinical diagnosis is essential while most of the posterior mediastinal tumors do not require any pre-operation clinical diagnosis. Surgery, surgery-chemoradiotherapy and chemoradiotherapy are the major methods of treatment for such tumors. For another thing, male gender was defined as a poor prognostic factor.