The treatment of patients with primary spontaneous pneumothorax remains controversial, since recurrence and the ultimate need for thoracotomy [corrected] cannot be predicted. In the current study, computed tomography (CT) of the lung was performed prospectively on 26 consecutive patients with primary spontaneous pneumothorax to determine whether the size and/or the number of apical blebs would correlate with recurrence and/or need for thoracotomy [corrected]. Both the number of blebs and the bleb score (calculated by the number of blebs multiplied by a numeric value assigned a range of bleb sizes) of the affected lung was significantly greater in patients with a history of recurrent pneumothorax and/or ultimate need for thoracotomy [corrected] as treatment. CT of the lung may be useful in predicting the natural history of pneumothorax.