We report on two patients with Proteus syndrome (PS), with emphasis on its pulmonary manifestations. The first patient was a 6-year-old girl diagnosed with PS at 5 years of age. The pulmonary abnormalities first observed at age 3 years and included streaky densities with accentuated vascular markings detected by chest radiography. The patient had persistent abnormalities on follow-up chest radiographs. Chest computed tomography (CT) scans showed diffuse pulmonary venous dilatations. The second patient was a 10-year-old boy diagnosed with PS at age 4 years. Chest radiography and CT scans showed patchy and streaky densities intermixed with small bullae, which were interpreted as pneumonia with post-inflammatory pneumatoceles. The patient developed diffuse enlargement of air spaces of the lungs at age 10 years with severe respiratory compromise. Although pulmonary manifestations in PS are uncommon, recognition of pulmonary vein malformation and the presentation of enlarged air spaces in the lungs at an earlier age are important for accurate diagnosis. The plain radiograph findings of accentuated vascular markings seen in patients with PS may appear similar to interstitial or chronic pneumonia. This report emphasizes the features of lung involvement in children with PS and suggests that specific attention be paid to pulmonary manifestations using chest CT scans. © 2011 Wiley-Liss, Inc.