Video-assisted thoracic surgery (VATS) is used in a growing range of pulmonary and mediastinal conditions. By avoiding thoracotomy, VATS is minimally invasive and allows shorter postoperative hospitalization. The advantages of video-assisted thoracoscopic techniques are obvious in the patients with severe cardiorespiratory failure. We investigated the role of CT before VATS. From September, 1991, to January, 1994, two hundred and eight patients were submitted to VATS: 80 pleurectomies, 63 lobectomies, 42 wedge resections, 11 bullectomies, 8 biopsies and 4 pneumonectomies were performed in patients with diffuse lung disease. All patients underwent conventional CT and an additional HRCT was performed in 164 patients. Bullae site, number, characteristics and size must be assessed. The possible relationship of bullae to impaired respiratory function must be studied. When nodules are present, their site, depth and relationship to fissures must be defined. With small and deep-seated nodules a thin snap-open mandrel device should be used for intraoperative detection. When lobectomies are contemplated, fissures must be accurately studied to assess their integrity and whether they completely separate the lobes. Fibrous adhesions can prevent pulmonary collapse; unfortunately, some of them cannot be detected by CT. Another limitation is the difficulty in assessing whether fissures are incomplete. To conclude, CT integrated with HRCT provides useful information for correct video-assisted thoracic surgical management.