This case-control study is based on an investigation of 27 nonsmoking patients with radiologically verified spontaneous pneumothorax (SP) and ten healthy never-smoker control subjects. The posteroanterior and lateral radiographs of patients and control subjects were normal. They were all submitted to the same clinical, laboratory, and radiologic examinations, including computed tomography (CT) of the lungs, with the aim of detecting any parenchymatous lung changes. Emphysema-like changes (ELCs) were detected on CT in 22 (81 percent) of the 27 patients, and if the ELC cases detected during interventional surgery are added, the frequency increases to 24/27 (89 percent). In 20 patients with unilateral SP, at least one ELC was found in 13 of the 20 SP-affected lungs, but only in five of the 20 lungs that were not diagnosed as having SP (p < 0.05). ELCs were found more frequently in the upper than in the lower lung regions (p < 0.05) and more frequently in the radiologically peripheral than in central regions (p < 0.001). No ELC was detected in the control group on CT. No alpha 1-antitrypsin deficiency was found in the 27 nonsmoking patients with radiologically verified SP who had ELCs despite the absence of these known promoters of emphysema.