Is organ donation important?
Donating organs can lengthen life or improve the quality of life, and therefore it is a genuine service to one's neighbor, provided no one is forced to do it. It must be certain that the donor during his lifetime gave his free and deliberate consent and that he was not killed for the purpose of removing the organ(s). Donation by living donors is also possible, for example, in bone marrow transplants or in the donation of one kidney. Organ donation from a cadaver presupposes a certain determination of death and the consent of the donor during his lifetime or else of his representative.
(Catholic Youth Catechism, question 391)