Are any kinds of Euthanasia morally permissible? If so, which ones and why?

I think it's a matter of personal opinion, but I believe it is not wrong when someone with a terminal, or excruciatingly painful or debilitating disease wants to end their suffering. Also, when infants are born with horrible genetic problems, like missing half their spine and skull or whatever, and they're going to die in a few days anyway, parents should be allowed to approve an injection of morphine or whatever. That's just my opinion.