Before you disregard the information that you are about to receive think about the logic involved because this is an important part of behavioral psychology that therapists don't deal with. Basically they don't have the skills. The skill required is to persuade a parent that the best response to this behavior is no response. In order for a behavior to continue, because it is of some value, it has to be rewarded. What ever your response is when he hits, it is rewarding to him. Otherwise he wouldn't do it.. You might as well hand him a piece of candy when he hits you. There is nothing that you can do short of possible severe corporal punishment to discourage this behavior, with certain important exceptions to be discussed later.
Behavior followed by a pleasant or desirable consequence(a reward) is likely to occur again. Behavior that is not followed by a reward will come to an end. It will extinghuish, go away like the dinosoars did. It is of no value. It accomplishes nothing. Being ignored is not a pleasant event. It is an unpleasant event. It is not something we enjoy. It is something we would prefer to avoid as we prefer to avoid any unpleasant event.

Let's assume that your child hits you. You are culturally bound to respond to that behavior. To at least say don't do that, it's bad. That is traditional parenting behavior. It is expected of you. However, your child is not normal If your child hits because he/she has ADHD or ADHD/ODD. He could care less about your opinion of right and wrong with regards to his behavior. He does what works for him and rational discussion or reasoning is a waste of breath and in fact makes matters worse as the joy he experiences from the defiance that he exhibits is very rewarding. In order for him to have this experience he has to provoke you into giving him a reprimand that has no affect on him at all. in terms of causing him to stop the behavior.
What if your child hit you and you did nothing. You looked away, said nothing, just stood there as if nothing occurred?
Whatever the reason for hitting you was didn't pay-off. Nothing changed. Of what value is that behavior if it accomplishes nothing?
There is more to the process. I will go on and finish if there is any interest. You are lucky the child is young. Do something now and be rid of it or it will continue to about age seven and get worse as time time goes on.
Rebounder