Perfusion scintigraphy is the most frequently used method for the regional assessment of pulmonary function in candidates for pulmonary resection with borderline respiratory function. This method provides two-dimensional images, and it considers all the segments of the pulmonary lobes as having the same volume and function, without considering the spatial overlapping of pulmonary areas with different function. As single-photon emission computed tomography (SPECT) provides tomographic imaging, this could be a more precise method for regional assessment.In this study, the postoperative predicted forced expiratory volume in one second (FEV1) (FEV1,ppo) was calculated in 26 patients with lung cancer using FEV1, quantitative lung perfusion scan with planar acquisition (PA) and quantitative lung perfusion scan with tomographic imaging (SPECT).The estimated FEV1,ppo values obtained using both methods were compared with FEV1 values measured after surgery (mean: 48¡44 days; range: 15-180 days; median: 32 days). The Pearson9s linear correlation coefficient was 0.8840 for FEV1,ppo estimated by PA and 0.8791 for FEV1,ppo estimated by SPECT. The linear correlation coefficient for lobectomy was greater than the coefficient for pneumonectomy using both methods.In conclusion, both methods show good correlation for real postoperative pulmonary function without demonstrating single-photon emission computed tomography superiority over planar acquisition, and both methods were more effective for estimating postoperative predicted forced expiratory volume in one second in lobectomies than in pneumonectomies. Eur Respir J 2004; 24: 258-262. Surgical resection is the treatment of choice for nonsmall cell lung cancer, and this therapy should be encouraged, as the prognosis worsens for patients who are not operated on. However, the removal of the lung parenchyma in patients, the majority of whom are smokers, and who have compromised cardiovascular and lung conditions, may cause deterioration in ventilatory function and lead to cardiopulmonary failure or death. Therefore, in these patients, a preoperative assessment is extremely important before the appropriate therapy is chosen [1][2][3][4].Pneumonectomy is well tolerated by the patient if: the forced expiratory volume in one second (FEV1) is either o2 L or w60% FEV1 predicted; the maximal voluntary ventilation (MVV) is w50% pred; the residual volume/total lung capacity ratio is either v0.5 or the carbon monoxide diffusion capacity of the lung is w60%. Lobectomy is well tolerated by the patient if: the FEV1 is o1 L and if the MVV is o40% pred. Nevertheless, many patients who could benefit from resection surgery show poor functional values that go against an indication for this surgery. In these cases other assessments are needed, such as perfusion or ventilation pulmonary scintigraphy, which are the most frequently used methods, as they provide a regional assessment of lung function and can be used to estimate postoperative pulmonary function, using the predicted postoperative...