Cystic fibrosis affects the lungs and also several other organs.

In the lungs, thick bronchial secretions block the small airways, which become infected and inflamed. As the disease progresses, the bronchial walls thicken, the airways fill with infected secretions, areas of the lung contract, and lymph nodes enlarge.

In the liver, thick secretions block the bile ducts. Stones may develop in the gallbladder.

In the pancreas, thick secretions may block the gland completely so that digestive enzymes cannot reach the intestine. The pancreas may produce less insulin, so some people develop diabetes (usually in adolescence or adulthood).

In the small intestine, meconium ileus (a type of intestinal blockage) can result from thick secretions and may require surgery in newborns.

The reproductive organs are affected by cystic fibrosis in various ways, usually resulting in infertility in males.

The sweat glands in the skin secrete fluid containing more salt than normal.