A 23-year-old man was admitted to the hospital because of dyspnea. Chest X-ray showed reticulo-nodular opacities. The crazy paving appearance on high-resolution CT was highly suggestive of pulmonary alveolar proteinosis. Histologic examination confirmed the diagnosis. Pulmonary alveolar proteinosis is a rare disease but an important diagnosis to make as treatment with pulmonary lavage is curative in a large proportion of patients.