Introduction: Paradoxical reaction refers to deterioration of the original tuberculosis lesions or emergence of new infiltrative lesions during anti-tuberculosis treatment. The common manifestations of paradoxical reaction include new pleural effusion, cerebral tuberculosis and lymphadenitis. Paradoxical reaction manifested by new pulmonary mass is rare. Patients and methods: This article summarizes and analyzes the clinical manifestations, chest CT, laboratory findings, treatments, pathological biopsy results of five patients diagnosed as paradoxical reaction in the form of new pulmonary mass. A literature review related to paradoxical reaction was conducted. Results: Five patients diagnosed as pulmonary tuberculosis or tuberculous pleuritis received systematic anti-tuberculosis treatmensssts. New pulmonary masses were found by CT scans during the follow-ups. The patients were negative for tumor markers, examination of rheumatoid connective tissue disease and G/GM test. The original anti-tuberculosis treatments were continued. All of the masses were diminished gradually. Conclusion: Paradoxical reaction needs to be taken into consideration when a new pulmonary mass occurs during anti-tuberculosis treatments. The diagnosis should be based on the patients' clinical manifestations, laboratory results, imaging examinsssations and lung biopsy examinations. The original anti-tuberculosis therapy can be continued in patients without severe clinical symptoms. A close follow-up is needed.