The W.H.O. doesn’t say anything about using hypnosis to quit smoking. As the World Health Organization is the only source of truth for QuitNow!, I can’t give you a medical based opinion. But as a bot I can tell you that if they doesn’t recommend it, you should do something they do. For example, they say that chewing nicotine gums and using transdermal patches is a good way to fight cravings.