Erdheim-Chester disease (ECD) is a rare proliferative non-Langerhans cell histiocytosis of multiple organs with unknown etiology. Around 20% of ECD cases are reported to be associated with lung involvement and there are very few cases manifested solely by nonspecific respiratory symptoms. A 50-year-old woman presented with dry cough and dyspnea for 2 weeks. Chest computed tomography (CT) revealed diffuse interlobular septal and fissural thickening with perilymphatic and subpleural nodular opacities, suggesting pulmonary lymphangitic spread of metastatic carcinoma. Bone scintigraphy and positron emission tomography/CT showed multiple skeletal and lymph node involvement. The patient underwent surgical lung biopsy and the pathologic feature was consistent with ECD. We describe this case to emphasize that ECD should be included in the differential diagnosis of cases suspected to have lymphangitic lung carcinomatosis. Moreover, the findings of positron emission tomography/CT scan, which showed hot uptakes in the affected areas, are also described.