Patients with continuous expansion of either giant lung cysts or areas of localized bullous emphysema will eventually deteriorate into a state of extreme respiratory distress due to compression of the remaining healthy pulmonary tissue. Thirty-one patients with these 2 types of lung disease having very poor respiratory function underwent surgery for the release of compromised healthy lung by resection of the expanding processes. A rational investigation program including respiratory tests, ventilation and perfusion scintigraphy and pulmonary angiography was gradually developed and analyzed. Surgical mortality was 12.9% in unilateral operations, probably somewhat higher in later contralateral interventions. The operative risk was higher in the emphysema group than in the group with giant lung cysts. Follow-up has demonstrated encouraging results in both groups concerning increased pulmonary function as well as improved working capacity.