Childhood constrictive bronchiolitis obliterans (CBO) is characterized clinically by the persistence of obstructive respiratory symptoms following a prolonged episode of lower respiratory viral infection. The diagnosis depends on the clinical, radiological and laboratory findings. Perfusion defects on scintigraphy may predict the severity. This report describes a 2-year-old girl who presented with a 15-day history of respiratory distress despite treatment. Auscultation of the lungs revealed prolonged expiration and bilateral crepitant rales. CXR revealed bilateral paracardiac infiltration. She improved with a treatment regimen of bronchodilators, systemic steroids and antibiotherapy; however, rales were detected again 10 days after discharge. HRCT of the lung revealed an oligaemic-mosaic pattern, more prominent in the left lung. The diagnosis of CBO was made on the basis of these clinical and radiological findings. Perfusion was normal in the right lung but diffusely decreased in the left lung on perfusion scintigraphy by Tc99m-MAA. Magnetic resonance (MR) angiography source images of the lungs revealed significant but not diffuse perfusion defects in the left lung, in contrast to radionuclide scintigraphy. There were areas of low perfusion in the right lung, which were not evident in radionuclide scintigraphy. The use of source images of MRI angiography of the lungs may be more sensitive and specific for the detection of perfusion defects in patients with CBO and may assist in determining the prognosis.