The CT including HRCT appearances of six patients with histopathologically confirmed pulmonary alveolar proteinosis（PAP） were evaluated and compared with those of chest radiographs In all patients the CT manifestations were quite similar: bilateral and diffuse airspace consolidation was usually patchy or confluent with sharply defined margins

intermingled with normal lung tissue The configuration of lung lesions was “geographical” in outline with angulate

strait and curved margins There were white branching linear opacities within the ground glass background Although various pulmonary diseases may mimic PAP in some way

a full awareness of the characteristic CT appearances of PAP is helpful in achieving a correct diagnosis CT may provide more accurate evidence than chest radiograph for the evaluation of the extent and delineation of PAP