A 42-yr-old woman was referred to our hospital because of multiple small nodules in a chest radiograph. She had no symptoms such as dyspnea, cough or sputum. A chest CT revealed many centrilobular small nodules and thin-walled cysts with predominance in the peripheral area of the lungs. The specimens obtained by thoracoscopic surgery showed granulomas with scattered eosinophils and numerous Langerhans' cells. The Langerhans' cells were positive for both S-100 protein and CD1a. These findings are compatible with pulmonary Langerhans' cell histiocytosis (LCH). Since the granulomas showed no fibrotic changes, the LCH may have been in its early stages. However, there were clusters of lymphocytes and macrophages around the terminal and respiratory bronchioles, and cystic lesions without cellular infiltrates, in the specimens. The former histologic findings suggested respiratory bronchiolitis causing interstitial lung disease and the latter are indistinguishable from centrilobular emphysema. Therefore, these smoking-related diseases may have been superimposed on the LCH in this patient.