[Show abstract][Hide abstract] ABSTRACT: Pulmonary cavity has infectious and non-infectious aetiologies. A 41-year old man was hospitalized with a 1-week history of productive cough, and pleuritic chest pain. A chest CT scan showed a cavitary lesion in left upper lobe. An open lung biopsy revealed the presence of connective tissue within alveolar ducts and bronchioles. In conclusion, cryptogenic organising pneumonia which is a rare cause of pulmonary cavitary lesion was diagnosed. The case was presented in order to emphasize such rare causes of cavitary lung lesions in the differential diagnosis of tuberculosis.