Cystic lung diseases constitute a distinct group of rare lung disorders, among which two result from monogenic defects affecting tumor suppressor genes: lymphangioleiomyomatosis, either sporadic or associated with tuberous sclerosis complex, and Birt-Hogg-Dubé syndrome. These disorders have similarities in their clinical expression, including occurrence in young adults, multiple pulmonary cysts, recurrent pneumothorax, skin hamartomas, and renal tumors. However, they markedly differ in their gender distribution, pathogenesis, disease course, and prognosis. Our knowledge on these two rare conditions is rapidly expanding. Management of lymphangioleiomyomatosis has substantially improved in the past decade with the understanding of its pathogenic mechanisms, the discovery of an effective therapy, and development of large cohorts and international guidelines. Birt-Hogg-Dubé syndrome has been described more recently and still awaits deeper understanding of its pathophysiology.