The aim of this prospective study was to evaluate: (1) the role of computed tomographic scanning in predicting chest wall invasion by peripheral lung cancer and (2) the results of operation according to the depth of chest wall involvement and other potential indicators of long-term survival. One hundred twelve patients with non-small cell lung cancer adjacent to the pleural surface who underwent computed tomographic scanning and subsequent thoracotomy were entered into this study. Tumor invasion was confined to the visceral pleura in 53 patients, to the parietal pleura in 18 patients, and to intercostal muscles in 25 patients; invasion extended beyond this layer in 16 patients. The computed tomographic criteria for chest wall invasion were (1) obliteration of the extrapleural fat plane, (2) the length of the tumor-pleura contact, (3) the ratio between the tumor-pleura contact and the tumor diameter, (4) the angle of the tumor with the pleura, (5) a mass involving the chest wall, and (6) rib destruction. The computed tomographic criteria 1 and 3 were significantly related to pathologic findings. Sensitivity was 85% for criterion 1 and 83% for criterion 3, specificity being 87% and 80%, respectively. Long-term survival of patients with T3 disease critically depended on the lymph node state and completeness of resection. The adenocarcinoma cell type and the T4 category were unfavorable prognostic factors. The depth of chest wall invasion did not affect survival, except for extensive rib and soft tissue infiltration. En bloc resection yielded better results than discontinuous resection.