Introduction & Objective: Thymoma is not a common tumor, but is one of the most common mediastinal neoplasms. Treatment strategies for different kinds of thymomas are controversial. In Iran few studies have been reported on this matter.Materials & Methods: Demography, clinical course, histopathology and progression free survivals (PFS) of 53 patients with thymoma were investigated retrospectively. Data analysis was done with Kaplan -Meyer method. Survival rate has been described according to PFS (survival between diagnosis and recurrence or death). Using log-Rank test, the difference between two groups of patients with invasive tumor and noninvasive tumor was studied.Results: Patients were 32 male and 21 female with mean age of 43 years (17-75 years). The most common symptoms were: cough (43.4%), dyspnea (39.6%), myastnenia (20.8%), weight loss (18.9%), and chest pain (17%).Most of tumors were in advanced stages. Treatment modalities were: surgery in 20.8%, surgery and chemoradiation in 66.8% and chemotherapy alone in 7.5% cases PFS results were 5.75+2.45 years.PFS between patients with invasive tumor and patients with non-invasive tumor did not show meaningful difference (P=0.616).Conclusions: In Iran, no definite protocol for therapy of thymoma has been recommended. Different modalities are used in our country. Although the principle method of treatment is surgery, other treatment modalities are used as well. Considering the slow growing pattern of this tumor, evaluation of different treatment modalities, need a prolonged follow up.