OBJECTIVES: The aim of this study was to assess the performance of four demand oxygen delivery systems (DODS) in improving oxygenation and effort tolerance, at rest and during exercise, in chronic obstructive pulmonary disease (COPD) patients. MATERIALS AND METHODS: Thirteen COPD patients were prospectively included. Four DODS (Oxiclip, Versatile, Venture and Impulse) were compared with continuous-flow oxygen (CFO). Nine of these patients performed 6-min walking tests on room air and on 3 l/min oxygen by DODS and CFO; Oxygen saturation, walking distance and the Borg dyspnea score were recorded. RESULTS: With all four DODS devices arterial oxygenation was improved with lower oxygen flow rates than with CFO. Oxygen economy was best with Impulse, but at a cost of less satisfactory oxygenation. Exercise desaturation was similar with CFO, Oxiclip, Venture, and Impulse but significantly higher with Versatile (P < 0.05). Borg dyspnea scores were similar with CFO, Oxiclip, Venture, and Versatile but worse with Impulse (P < 0.05). There was no significant difference in walking distances. CONCLUSIONS: All four DODS improved oxygen saturation and saved oxygen. However, performance was better with the two devices (Oxiclip and Venture) that deliver a bolus of oxygen at inspiration onset.