Abstract Funding Acknowledgements Type of funding sources: None. Background A cardiopulmonary exercise testing (CPET) is recommended before a resection of a primary pulmonary nodule by surgical approach for patients at risk (with abnormal spirometry). The maximal oxygen consumption measurement (VO2max) evaluates the morbidity/mortality and allows to orient the surgical choice towards a lobectomy or a cuneiform resection. However, the VO2 max can be influenced by some parameters as patient’s motivation, overweight, …. Purpose The objective of this work is therefore to identify other complementary predictive factors of cardiopulmonary exercise test (CPET) in at-risk patients population with abnormal pulmonary function tests. Methods 211 subjects who underwent thoracic surgery for non-small cell lung cancer (NSCLC) between 2016 and 2020 at Erasmus Hospital and performed a CPET were analyzed and divided into 2 groups (G1 At Risk: n = 159: 10 mL/min/kg < VO2max < 20 mL/min/kg; G2 Control: n = 52: VO2max ≥ 20 mL/min/kg). Anthropological, biometric, clinical, and intraoperative data were collected based on the medical record. Results The risk group (G1) had a reduced VO2max associated with a higher VE/VCO2 slope. However, the 30-day and 1-year mortality as well as the number of minor and major complications were comparable to the control group (G2) because of the screening and the operative choices. All groups combined, VO2max was predictive of major complications (OR = 0.98, p = 0.04) and VE/VCO2 slope emerged as a predictor of total and minor postoperative complications (OR = 1.07, p = 0.0054 and respectively OR = 1.05, p = 0.046). Patients with a slope ≥ 34.5 had a higher incidence of total complications (OR = 3.16, p = 0.0004). In a subgroup with medium operative risk (VO2max between 15 and 20 mL/min/kg), VE/VCO2 slope was predictive of total complications (OR = 1.09, p = 0.02) whereas VO2max was predictive of major complications (OR = 0.97, p = 0.04).