In this prospective study, the value of computed tomography (CT) in detecting bullae and bleb formation of the lung in 35 patients with primary spontaneous pneumothorax (PSP) has been determined. The ability of CT in the detection of bullae and bleb formation and fibrotic changes is compared with the chest film in PSP. CT showed pathological lung changes in 31/35 patients. In most cases, few (n < 5) and small blebs (i.e., < 2 cm in diameter) were found. In 16/35 cases, blebs (< 2 cm) and bullae (> 2 cm in diameter) occurred in the extra-apical region. Contralateral pathological changes were found in 23/35. Bullae (> 2 cm) could be detected only in 6/35. In the chest film, bullae and blebs could be detected in 11/35 cases on the ipsilateral (in 2/35 cases not confirmed by CT), in 3/35 on the bilateral and in 4/35 only on the contralateral side. Thus, CT was proved to be of high value in the assessment of bullae and bleb formation in PSP compared with chest film. Negative pressure drainage was instituted as primary therapy. In a follow-up of 9.6 (+/- 5.7 SD) months, only early recurrences were noticed (n = 35). The rate of recurrences was 6/35 patients. The longer follow-up period (mean 31.7 +/- 6.1 months) could be performed for 32 patients; 3 were lost. Additionally, 2 recurrences occurred. No correlation between recurrences and anatomical status (number, size and distribution of blebs/bullae) as assessed by CT was found. Differential treatment protocols on the basis of the initial findings do not appear to be warranted.