Purpose of review Supplemental oxygen improves survival in patients with chronic obstructive pulmonary disease (COPD) and severe hypoxaemia, but the effect of oxygen therapy in mild or moderate hypoxaemia to reduce symptomatic chronic breathlessness remains unclear. This review provides an overview of recent evidence about the role of oxygen therapy for the relief of chronic breathlessness in advanced illness. Recent findings In COPD, a recent Cochrane review strengthens earlier findings regarding the positive effect of supplemental oxygen compared with air during exercise test in the training setting. The novel analysis of effect of oxygen therapy on quality of life (QoL) showed no clear effect. Short-burst oxygen therapy given before exercise had no effect and should not be used. Summary Supplemental oxygen during exercise has been shown to reduce breathlessness in patients with COPD who have no or mild hypoxaemia, but it is not clear whether the reduction in breathlessness shown in the laboratory setting translates into a clinically important benefit. Further studies are needed to establish this.