Two cases of pulmonary lymphangiomyomatosis are reported and findings of high resolution computed tomography (CT) are described. CT reveals that most lesions appearing reticular or emphysematous on radiographs are actually cysts, and accurately displays the extent and distribution of cystic change of the lung. On high resolution CT, individual cystic walls are much better displayed than on routine 10 mm section CT. Further, it is possible to detect even trivial pleural effusion and mediastinal lymph node swelling by CT.