A 10-year-old boy was referred to our department for computed tomography of the thorax because of chronic cough, fever and progressive dyspnea. His chest X-ray showed bilateral, diffuse reticulonodular shadowing. Computed tomographic scan of the thorax demonstrated bilateral, diffuse and punctuate pulmonary nodules with patchy ground-glass appearances (Figure A). The nodules caused a pulmonary tree in the 3D images. In fact, the pulmonary tree was an air bubble (Figure B). Despite antibiotic therapy, the symptoms persisted. Laboratory examination revealed an ESR rate of 42 mm per hour. Leukocyte count and C-reactive protein levels were both normal. The patient’s previous history revealed that he previously had pigeon breeder’s disease. Pigeon breeder’s disease rarely occurs in childhood. The disease typically appears in the bronchioles and causes alveolar type III - type IV allergic reactions [1]. The patient’s history, especially the existence of chronic cough and progressive dyspnea and clinical examination showed wheezing crackles and abnormal laboratory values. Chest X-ray, MDCT findings and lung function tests demonstrated a restrictive defect, and tracing the specific IgG precipitins in the breeder’s serum suggests the diagnosis of pigeon breeder’s disease [2]. MDCT is a reliable tool for diagnosing the presence and severity of pigeon breeder’s disease.