Tree-in-buds of bronchiolitis obliterans in a 28-year-old woman. Bronchiolitis obliterans was diagnosed on spirometry and transbronchial lung biopsy 16 months after bone marrow transplantation for chronic myelocytic leukemia. Inspiratory high resolution computed tomography scan shows decreased lung attenuation and subsegmental bronchial dilatations in left lower lobe. Tree-in-bud pattern is noted in subpleural portion of posterior basal segment of left lower lobe (arrow).