To determine the extent to which younger COPD patients improve their cardiorespiratory function during exercise in comparison with older COPD patients, as a result of exercise training. Thirty-nine COPD patients underwent an exercise program. They were divided into two groups: a younger group (57.2+/-1.0 years, n=18 patients) and an older group (68.8+/-0.6 years, n=21 patients). Forced expiratory volume in 1s was lower than 55% of the predicted value for all patients. After training, VO2 symptom-limited significantly improved by 10.3% and 8.4% for the younger and older COPD patients, respectively (P<0.05). Peak power significantly improved by 25.2% and 17.8% in the younger and older groups, respectively (P<0.05) with a greater improvement for the younger group (P<0.05). At submaximal exercise, ventilation and heart rate significantly decreased after training in the younger COPD patients (P<0.05) with no significant modification in the older COPD patients. The results suggest that all patients with COPD benefit from exercise rehabilitation at maximal exercise workload, however, according to their age, submaximal cardiorespiratory adaptations were greater in younger patients.