The "crazy-paving" pattern is a common finding at thin-section computed tomography (CT) of the lungs. It consists of scattered or diffuse ground-glass attenuation with superimposed interlobular septal thickening and intralobular lines. This finding has a variety of causes, including infectious, neoplastic, idiopathic, inhalational, and sanguineous disorders. Specific disorders that can cause the crazy-paving pattern include Pneumocystis carinii pneumonia, mucinous bronchioloalveolar carcinoma, pulmonary alveolar proteinosis, sarcoidosis, nonspecific interstitial pneumonia, organizing pneumonia, exogenous lipoid pneumonia, adult respiratory distress syndrome, and pulmonary hemorrhage syndromes. Knowledge of the many causes of this pattern can be useful in preventing diagnostic errors. In addition, although the causes of this pattern are frequently indistinguishable at radiologic evaluation, differences in the location of the characteristic attenuation in the lungs, as well as the presence of additional radiologic findings, the patient's history, and the clinical presentation, can often be useful in suggesting the appropriate diagnosis.

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