Recent studies have used preoperative cardiopulmonary exercise testing to improve risk assessment of pulmonary resection for lung cancer. These studies have demonstrated inconsistent correlation between peak oxygen uptake (VO2) and postoperative complications but have not systematically examined other methods of risk stratification. We analyzed the findings in 42 patients who had cardiopulmonary exercise testing prior to lung cancer resection. Preoperative clinical data combining pulmonary factors (obesity, productive cough, wheezing, tobacco use, ratio of the forced expiratory volume in 1 s over the forced vital capacity [FEV1/FVC] < 70 percent, and PaCO2 > 45 mm Hg), and an established cardiac risk index were used to generate a cardiopulmonary risk index (CPRI). When analyzed using the risk index, the incidence of postoperative complications increased with higher CPRI scores. Those with a CPRI of 4 or greater were 22 times more likely to develop a complication, compared to a CPRI of less than 4 (p < 0.0001). We found that patients with a peak VO2 less than 500 ml/m2/min (body surface area) were 6 times more likely to experience a cardiopulmonary complication (p < 0.05). With multiple logistic regression analysis, peak VO2 was not an independent predictor of postoperative complications. Analysis also demonstrated that a CPRI of 4 or greater was associated with significant reductions in peak VO2. We conclude that both the peak VO2 during cardiopulmonary exercise testing and a multifactorial CPRI are highly predictive of complications after lung resection. Adding the peak VO2 did not enhance the risk estimation generated by the CPRI. The association between postoperative complications and peak VO2 may be explained by the correlation between identifiable cardiopulmonary disease (CPRI) and reduced oxygen uptake with exercise.