Follicular bronchitis/bronchiolitis is pathologically characterized by peribronchiolar lymphoid follicles, which is one of reactive pulmonary lymphoid disorders. It is associated with 1) the result of infections such as mycoplasma, chlamydia etc., 2) immunodeficiency syndromes, 3) connective tissue diseases such as rheumatoid arthritis and Sjogren's syndrome and 4) local or systemic hypersensitivity reaction. And it can be also developed without obvious causes and associated diseases(idiopathic). Radiologically it represents as bilateral interstitial patterns of pulmonary infiltrates. In this case, a 49 year-old woman was presented with intermittent cough and sputum. On chest X-ray and CT, 5 x 4 cm sized mass in right upper lobe and paratracheal lymphadenopathies were detected, by which lung malignancy was suspected. Bronchoscopy, transbronchial lung biopsy and transthoracic needle aspiration showed non-specific findings only. After right upper lobectomy, we could confirm a case of follicular bronchiolitis which presented as an unusual mass-like radiologic finding.