Emphysema, ehm fuh SEE muh, is a lung disease in which victims have difficulty breathing, especially when they exhale. Emphysema is one of the two main forms of chronic obstructive pulmonary diseases. The other is chronic bronchitis (see Bronchitis). Most people with chronic obstructive pulmonary diseases suffer from both emphysema and chronic bronchitis. Chronic obstructive pulmonary diseases are characterized by progressive narrowing of the airways--that is, the tubes that connect the lungs to the nose and mouth.