Eight observations of diffuse pulmonary leiomyomatosis in women were studied. This disease in a number of cases was combined with leiomyoma of the uterus. The clinical picture depends to a certain extent on which structural part of the pulmonary tissue is the predominant source of tumor growth. Disorders in the lymphatic system causes chylous pneumothorax. Hyperplasia of smooth muscle fibers occurs multicentrically: in interalveolar septae, along the small bronchi and bronchioli, in the walls of small blood and lymph vessels, intrathoracic lymph nodes. Leiomyomatosis of the lungs is of neoplastic nature, most likely of dyshormonal genesis.