Objective:To study the clinical characteristics and diagnosis of primary pulmonary lymphoma(PPL).Methods:A retrospective review was performed based on the clinical records of 18 PPL cases treated at Affiliated Pulmonary Hospital of Tongji Uni- versity from 1999 Sep to 2006 June.The clinical manifestations,imaging features,diagnosis approaches,staging,and prognosis of the 18 patients were analyzed.Results:All the eighteen cases of PPL belonged to the non Hodgkin(?) lymphoma.There were 13 patients with mueosa-associated lymphoid tissue(MALT)lymphoma,3 patients with small B cell lymphoma,1 patient with anaplastie large cell lym- phoma,and 1 patient with T cell lymphoma tendency.The main symptoms were cough and weight loss.The PPL in 4 patients with non specific symptoms were diagnosed daring physical examination.Pulmonary consolidation shadows and multiple nodules were the main findings of CT scan.An air bronehogram is often seen in the consolidation imaging.All the 18 patients received fiber-bronchoseopie bi- opsy but only 2 patients were diagnosed as PPL.Seven patients were given percutaneous needle biopsy but PPL was confirmed in only 1 patient.The diagnosis was confirmed in fifteen patients by operative pathology.Ten patients received open thoraeotomy and 5 patients received video-assisted thoracoscopy.Of the 15 patients,there were 9 cases in stage E,4 cases in stageⅡ1E,3 cases in stageⅡ2E,1 case in stageⅢ,and 1 case in stageⅣ.Surgery,radiotherapy,and chemotherapy were most common treatment modalities for PPL. Conclusion:PPL was easy to be misdiagnosed due to non specific clinical and imaging manifestations.The invasive biopsy is the main diagnosis approach.The prognosis is relatively better.