Emphysema is a form of chronic (long-term) lung disease and is the main type of chronic obstructive pulmonary disease (COPD). People with emphysema have difficulty breathing due to a limited ability to blow air out. There are multiple causes of emphysema, but smoking is by far the most common. Emphysema has no cure, but quitting smoking may slow its progression. Follow the links below to find WebMD's comprehensive coverage about emphysema, what it looks like, how to treat it, and much more.