Abstract Objective: The objective of the present study was to assess whether patients unable to perform a preoperative maximal stair climbing test had an increased incidence of morbidity and mortality after major lung resection compared to patients who were able to exercise. Methods: Three hundred and ninety one patients submitted to pulmonary lobectomy or pneumonectomy for lung cancer were analyzed. Forty-five of these patients were unable to perform a preoperative maximal stair climbing test for underlying comorbidities. Unadjusted and propensity score case matched comparisons were performed between patients who could and who could not perform a preoperative stair climbing test. Multivariable analyses were then performed to identify predictors of morbidity and mortality, and were validated by bootstrap bagging. Results: Patients who could not perform the stair climbing test had similar morbidity rates (31.1 vs. 35.6%, respectively, PZ0.7), but higher mortality rates (15.6 vs. 4.4%, respectively, PZ0.08) and deaths among complicated patients (50 vs. 12.5%, respectively, PZ0.025), compared to propensity score matched patients who could perform the stair climbing test. Logistic regression analyses showed that the inability to perform the stair climbing test was an independent and reliable predictor of mortality (PZ0.005) but not of morbidity (PZ0.2). Conclusions: Patients unable to perform a preoperative maximal exercise test had an increased risk of mortality after major lung resection. Half of these patients did not survive postoperative complications, due to their decreased aerobic reserve caused by physical inactivity which made them unable to cope with the increased oxygen demand.