In most cases, signing up for cryonics and signing up as an organ donor are not mutually exclusive. The manner of death most suited to organ donation (rapid brain death with (parts of) the body still in good condition, generally caused by head trauma) is not well suited to cryonic preservation. You'd probably need a directive in case the two do conflict, but such a conflict is unlikely.

Alternatively, neuropreservation can, at least is theory, occur with organ donation.