Breathing techniques are included in the rehabilitation program of patients with chronic obstructive pulmonary disease (COPD). The efficacy of breathing techniques aiming at improving symptoms of dyspnea and eliciting physiological effects is discussed in this paper. In patients with COPD, breathing techniques aim to relieve symptoms and ameliorate adverse physiological effects by: 1) increasing strength and endurance of the respiratory muscles; 2) optimizing the pattern of thoracoabdominal motion; and 3) reducing dynamic hyperinflation of the rib cage and improving gas exchange. Evidence exists to support the effectiveness of pursed lips breathing, forward leaning position, active expiration and inspiratory muscle training, but not for diaphragmatic breathing. Careful patient selection, proper and repeated instruction and control of the techniques, and assessment of the effects are necessary. Despite the evidence that breathing techniques are effective, several problems need to be resolved. The limited evidence for the transfer of the effects of breathing techniques during resting conditions to exercise conditions raises several questions. Do breathing techniques have to be practiced during activities of daily living?