Hypnotherapy is very effective in helping people to become a non-smoker, or returning to being a non-smoker as I would put it. People start smoking and continue to smoke for a whole host of reasons, but it is usually based around the belief that smoking makes that person feel better in some way. That can be in the way of relieving stress, suppressing appetite, fitting in socially and many more.
Hypnotherapy addresses the root cause of why the client has been continuing to smoke. It can also be used to create an aversion to the smell and /or taste of cigarettes if the client wishes.