A 7-year-old girl presented to the pediatric intensive care unit following a craniotomy that left her with dysphagia, poor cough, and problems with retained secretions. Pulmonary function and blood oxygen saturation worsened for 3 days after surgery. Noninvasive positive-pressure ventilation and increased fraction of inspired oxygen improved oxygenation. Glycopyrrolate was administered to decrease secretions but had little effect. The first chest radiograph showed left lung hyperinflation. The right lung showed loss of volume and elevation of the right hemidiaphragm. There was no mediastinal shift. Another chest radiograph 3 hours later showed substantial improvement. We discuss the causes of acute lung volume asymmetry and possible interpretations of the radiographs.