The most important preoperative cardiopulmonary variables for identifying patients at increased risk prior to lung resection are: FEV1, FEV1-ppo, DLCO, MVO2, and SO2. The aim of this study was to evaluate the ability and usefulness of predictive postoperative FEV1 (FEV1-ppo) in 80 patients undergoing lung resection. Spirometry was performed before and 6 months after operation; residual respiratory function was calculated using Nakahara's formula, and data analysis calculations were performed using the chi 2 test. It was observed that the resulting predictive values were almost comparable to the values observed 6 months postoperatively in 63.75% of patients and the correlation proved statistically significant (P < 0.005). In view of its simple and rapid execution, we conclude that Nakahara's formula, compared with the others, remains a reliable standard method of assessing high-risk patients and planning appropriate surgery.