A complicated, high-risk surgical procedure in which a healthy lung or lungs replace damaged or diseased lungs. Lung transplantation is performed only as a lifesaving measure on people who have not responded to other treatment options, will not survive without the transplant, and have a high probability of a positive outcome from the transplant. Most people who successfully receive a transplanted lung or lungs can recover to live relatively normal lives, but long-term outcomes are not yet known. Single lung transplantation is more common than bilateral lung transplantation. Finding appropriate donor lungs is difficult because the organs must match exactly the recipient’s body size, blood type, and tissue.