Aim: Mediastinum is the body compartment between two thoracic cavities. Due to its rich tissue variability, vascularity and lymphatic tissue content, mediastinum is a place for primary and secondary masses and cysts. In this study, the role of surgery for the diagnosis and treatment of mediastinal tumors and cysts, were investigated. Method: Eighty six patients who admitted to our clinic with diagnosis of primary mediastinal cysts and tumors between July 2002 and July 2009 were investigated. All of the patient were analysed retrospectively for age, gender, complaint, lesion localization, surgical procedure and histopathological diagnosis. Result: Tumor- cyst excision was performed for primary mediastinal masses in 86 patients. There were 44 (51%) women and 42 (49%) men, aged from 5 to 78 (mean age was 48,03). Most of the lesions were located in the anterior mediastinum (50%). Thirty seven of the cases did not have any complaints. Chest pain (26.7%), cough (23.5%) and shortness of breath were common complaints. Definitive diagnosis was obtained in all of the patients by right/left thoracotomy (41.9%/10.5%), sternotomy (25.6%) or mediastinoscopy (4.7%). Discussion: Although lession location and clinical findings are helpful in determination of mediastinal cysts and tumors, tissue diagnosis is almost always required. Surgery is compulsory for adequate tissue sampling and it is stil the most important therapautic procedure. ©Copyright 2014 by Gazi University Medical Faculty.