To test the predictive value of stairs climbing test for the development of postoperative complications in lung cancer patients with forced expiratory volume in one second (FEV1)<2 L, selected for an elective lung surgery. The prospective study was conducted in 101 consecutive patients with an FEV1<2 L selected for elective lung surgery for lung cancer. Preoperative examination included medical history and physical examination, lung function testing, electrocardiography, laboratory testing, and chest radiography. All patients underwent stairs climbing with pulse oximetry before the operation with the number of steps climbed and the time to complete the test recorded. Oxygen saturation and pulse rate were measured every 20 steps. Data on postoperative complications including oxygen use, prolonged mechanical ventilation, and early postoperative mortality were collected. Eighty-seven of 101 patients (86%) had at least one postoperative complication. The type of surgery was significantly associated with postoperative complications (25.5% patients with lobectomy had no early postoperative complications), while age, gender, smoking status, postoperative oxygenation, and artificial ventilation were not. There were more postoperative complications in more extensive and serious types of surgery (P<0.001). The stairs climbing test produced a significant decrease in oxygen saturation (-1%) and increase in pulse rate (by 10/min) for every 20 steps climbed. The stairs climbing test was predictive for postoperative complications only in lobectomy group, with the best predictive parameter being the quotient of oxygen saturation after 40 steps and test duration (positive likelihood ratio LR, 2.4; 95% confidence interval CI, 1.71-3.38; negative LR, 0.53; 95% CI, 0.38-0.76). In patients with other types of surgery the only significant predictive parameter for incident severe postoperative complications was the number of days on artificial ventilation (P=0.006). Stairs climbing test should be done in routine clinical practice as a standard test for risk assessment and prediction of the development of postoperative complications in lung cancer patients selected for elective surgery (lobectomy). Comparative to spirometry, it detects serious disorders in oxygen transport that are a baseline for a later development of cardiopulmonary postoperative complications and mortality in this subgroup of patients.