Purpose : The purpose of this study was to evalate the effectiveness of percutaneous fine-needle aspiration(PCNA) in malignant and benign mediastinal lesions. Materials and Methods : PCNA of mediastinal lesions wereperformed in 46 patients using 22 Guage thin-walled Westcott type needle under fluoroscopy guidance. there were 24malignant mediastinal masses, 18 of which were diagnosed only by PCNA and six of which were proven surgically. of22 benign mediastinal masses, 19 cases were proven surgically. Results : In 24 patients with malignant neoplasms,a positive diagnosis of malignancy was established in 18 (75%). One suspicious malignancy and five falsn negativeresults occurred. In 22 patients with benign masses, a specific diagnosis was established in six (27.3%), and 13patients revealed nonspecific benignanay (59.1%). Three benign masses were reported as unsatisfactory. Fivepatients developed pneumothorax as a complication, and one of these neeeded a chest tube. Conclusion :Percutaneous fine-needle aspiration in mediastinal masses can differentiate benign mass from malignancy and canmake a pathologic diagnosis.