Dyspnea is a major symptom of patients with chronic respiratory diseases leading to activity limitation, deconditioning and a decreased quality of life. It results from impairments in gas exchange, balance between the load on and capacity of the respiratory muscles and increased neural respiratory drive. It can be distinguished from hypoxic failure due to disturbances in gas exchange, e.g. in pulmonary fibrosis and hypercapnic failure of the ventilatory pump, e.g. in chronic obstructive pulmonary disease (COPD) or kyphoscoliosis. Medical history and physical examination are the mainstays of diagnostic evaluation. In addition specific laboratory, radiographic and clinical examinations are performed depending on the symptoms and the diagnostic possibilities. In patients with chronic lung diseases, e.g. COPD, pulmonary fibrosis or pulmonary hypertension, dyspnea often progresses relentlessly with time to reach incapacitating levels. Therefore, the diagnosis is frequently made late in the course of the disease. In patients with malignancies dyspnea is a frequent symptom, which, however, is less recognized than pain. Treatment goal of dyspnea in chronic lung diseases is relief of dyspnea. Depending on the underlying disease a combination of medical therapy, symptomatic treatment, noninvasive ventilation and physical training can be applied.