Dyspnoea, defined as a sensation of an uncomfortable awareness of breathing, is one of the most frightening and distressing symptoms for patients with cancer. It is very common in cancer patients with and without direct lung involvement. The gold standard of diagnosis and assessment is the patient's self-report. Measurements of respiratory rate, oxygen saturation, and arterial blood gases do not measure dyspnoea. Fast, safe, and effective relief of the symptom is possible whether or not identifiable reversible causes exist. Opioids are the first line of therapy for such relief. Medical management can be directed at the underlying cause when the potential benefits outweigh the burdens of such treatment. In rare cases for which symptomatic treatment does not control dyspnoea to the patient's satisfaction, sedation is an effective, ethical option.