Background and objective In this era of increasing options for treatment of ‘surgical’ lung cancer patients, preoperative physiologic assessment of accurate patient selection is becoming more important. The variability in an objective measure of cardiorespiratory fitness (peak oxygen consumption (VO2peak)) across performance in operable non-small-cell lung cancer (NSCLC) patients enrolled in the Cancer and Leukemia Group B trial was compared. Methods Using a cross-sectional design, 392 NSCLC patients underwent an incremental cardiopulmonary cycling exercise test to symptom limitation with expired gas analysis to determine VO2peak. Performance status (PS) was assessed using the Eastern Cooperative Oncology Group (ECOG) tool. Results There was a significant decrease in VO2peak across increasing ECOG categories (P