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A 34 -year-old man was admitted to the hospital because of chronic cough. Pulmonary radiogram showed a cavitary coin lesion and he underwent surgical excision. Histologically bronchiolitis obliterans organizing pneumonia (BOOP) was reported but no etiology is found. After excision, bilateral pulmonary micronodules which had been previously seen on the computer tomography regressed spontaneously. In the differential diagnosis of cavitary solitary lesions, BOOP is a rare entity. The case is discussed with a review of the literature.