Exertional dyspnea scales (EDS) and health-related quality-of-life questionnaires (HRQoLQs) are used to assess chronic obstructive pulmonary disease (COPD). The GOLD guidelines categorize patients according to either 1 of these 2 domains, the lung function and the frequency of acute exacerbations in the preceding year, however with inconsistent results. Combining EDS and HRQoLQs may yield better results; however, the best combination is unclear. Whether the EDS quantifies the exercise capacity or the dyspnea perception is also unclear. The study was designed to correlate the EDS with exercise capacity and dyspnea perception and to evaluate the best combination of the EDS and HRQoLQ.Three EDS were compared by exercise capacity and Borg scores at rest and during exercise in 57 patients with COPD. Three HRQoLQs were compared by 4 domains of clinical assessments, and 2 types of exercise. The strength of correlation |r| was categorized by quartiles from <0.3 to ≥0.6.The EDS was better correlated with exercise capacities (|r| = 0.29-0.65, P < 0.05-<0.0001) than with the resting and exertional Borg scores (|r| = 0.08-0.55, P = NS- <0.0001). The EDS were moderately to strongly interrelated, but this correlation was weaker when including Oxygen-cost Diagram (OCD) (with the modified Medical Research Council, mMRC r = -0.56, with the baseline dyspnea index, BDI r = 0.49 vs. mMRC with BDI r = -0.73); however, the OCD had the strongest correlation with walking distance (r = 0.65, vs mMRC r = -0.59, BDI r = 0.5) and peak oxygen uptake (r = 0.39 vs mMRC r = -0.29, BDI r = 0.36). Among the HRQoLQs, the COPD assessment test (CAT) was most strongly correlated with the St. George Respiratory Questionnaire (SGRQ) (r = 0.77) and similar to the SGRQ regarding significant correlations with the other instruments (|r| = 0.29-0.67 vs. 0.36-0.77) but poorly with walking distance (r = -0.02). The OCD was mildly correlated with the CAT (r = -0.4).The EDS was more related to the exercise capacity than to the dyspnea perception and the CAT was most closely related to the other instruments but poorly with walking distance. The OCD can be used to compensate for this weak correlation. The study suggests using the CAT and the OCD simultaneously when undertaking clinical evaluation of patients with COPD.