This monograph written in Spanish deals with 17 cases of cystic disease of the lung observed by the author, who is professor of pediatrics at the University of Habana, over a period of ten years. He believes that the condition is a congenital malformation due to mesodermic hyperplasia in which the affected zones remain in the fetal stage of development. The prognosis is unfavorable and in small children grave. The only satisfactory treatment is surgical removal of the areas (lobectomy or pneumectomy).