This paper reports the results of a retrospective study undertaken to assess the reliability of regional ventilation-perfusion pulmonary scanning in predicting the remaining respiratory function (pFEV1), and the early and long-term outcome of 33 patients with chronic airways disease, submitted to pulmonary resection at the 1st Department of Surgery. All patients had been diagnosed as resectable with the traditional tools and had a traditional pFEV1 (tpFEV1) greater than 800 ml. All pFEV1 were re-calculated (npFEV1) with our new formula which also includes as lost for function all lung areas not to be resected with V/Q mismatching. Normal perfusion and ventilation distribution was found in 24.2% of patients in the lesion area and in 33.3% in the remaining pulmonary areas. An impairment of perfusion was observed in the lesion area in 72.7% of patients, in the remaining areas in 48.4%. An impairment of ventilation was observed in the same regions in 66.6% and 48.5% of patients, respectively. Abnormality in ventilation/perfusion matching occurred in the lesion area in 15.2% of cases, in the ipsilateral lung areas in 18.2%, in the contralateral lung in 48.4% of cases. In predicting postoperative FEV1, and early and long-term mortality among our resectable patients, the tpFEV1 showed an accuracy of 91%, an index of resectability of 93.7%, of unresectability of 0%. Our npFEV1 reached an accuracy of 94.4%, an index of resectability of 100% and an index of unresectability of 66.7%.