Breathelssness (Dyspnea) is a cardinal symptom in patients with chronic obstructive pulmonary disease (COPD), often triggered by daily-life physical activities. Despite optimal treatment of the underlying disease, many patients still suffer from chronic and disabling dyspnea for many years, leading to exercise intolerance, and worse morbidity and mortality. To date, an effective pharmacologic treatment to relieve chronic dyspnea is lacking. Recent pilot data support that inhaled L-menthol can markedly decrease laboratory-induced dyspnea in COPD patients, likely through increased afferent feedback of airflow in the airways by inducing a cooling sensation through olfactory stimulation. The aim of this study is therefore to assess the effectiveness and mechanisms of inhaled menthol for relief of chronic dyspnea in patients with COPD.