Although some lung cysts in infancy may be harmless and the pathology reversible, many of these lesions seriously jeopardize life by causing compression atelectasis with pneumonia, by enlarging to sizes incompatible with adequate respiratory function, or by becoming grossly infected. In such instances, surgical removal becomes urgent. The three cases of this disease seen at Colorado General Hospital in the past six years illustrated these complications, and all required surgical intervention. Lung cysts in infancy, if they are symptomatic, should be surgically removed, preserving as much pulmonary parenchyma as possible.