Breathing exercises for people with chronic obstructive pulmonary disease (COPD) aim to alter respiratory muscle recruitment, improve respiratory muscle performance and reduce dyspnoea. Although some studies have reported positive short-term physiological effects of breathing exercises in people with COPD, their effects on dyspnoea, exercise capacity and well being are unclear. To determine whether breathing exercises in people with COPD have beneficial effects on dyspnoea, exercise capacity and health-related quality of life compared to no breathing exercises in people with COPD; and to determine whether there are any adverse effects of breathing exercises in people with COPD. The Cochrane Airways Group Specialised Register of trials and the PEDro database were searched from inception to October 2011. We included randomised parallel trials that compared breathing exercises to no breathing exercises or another intervention in people with COPD. Two review authors independently extracted data and assessed the risk of bias. Primary outcomes were dyspnoea, exercise capacity and health-related quality of life; secondary outcomes were gas exchange, breathing pattern and adverse events. To determine whether effects varied according to the treatment used, we assessed each breathing technique separately. Sixteen studies involving 1233 participants with mean forced expiratory volume in one second (FEV(1)) 30% to 51% predicted were included. There was a significant improvement in six-minute walk distance after three months of yoga involving pranayama timed breathing techniques (mean difference to control 45 metres, 95% confidence interval 29 to 61 metres; two studies; 74 participants), with similar improvements in single studies of pursed lip breathing (mean 50 metres; 60 participants) and diaphragmatic breathing (mean 35 metres; 30 participants). Effects on dyspnoea and health-related quality of life were inconsistent across trials. Addition of computerised ventilation feedback to exercise training did not provide additional improvement in dyspnoea-related quality of life (standardised mean difference -0.03; 95% CI -0.43 to 0.49; two studies; 73 participants) and ventilation feedback alone was less effective than exercise training alone for improving exercise endurance (mean difference -15.4 minutes; 95% CI -28.1 to -2.7 minutes; one study; 32 participants). No significant adverse effects were reported. Few studies reported details of allocation concealment, assessor blinding or intention-to-treat analysis. Breathing exercises over four to 15 weeks improve functional exercise capacity in people with COPD compared to no intervention; however, there are no consistent effects on dyspnoea or health-related quality of life. Outcomes were similar across all the breathing exercises examined. Treatment effects for patient-reported outcomes may have been overestimated owing to lack of blinding. Breathing exercises may be useful to improve exercise tolerance in selected individuals with COPD who are unable to undertake exercise training; however, these data do not suggest a widespread role for breathing exercises in the comprehensive management of people with COPD.