My almost 9yr old has serious trouble making friends...?

I have an almost 9yr old son with ADHD, and as he gets older he is having alot more trouble making friends at school. He goes from one extent to the other being a crazy twit and tending to scare kids off i think, to being totally withdrawn and not game enough to say hello to a young boy who has said he would like to be my sons friend. He doesn't have any 'friends' as far as i can tell from what he says but when he is hanging around with kids it's only with girls, i myself dont have a problem with this but i think its also what is making him stand out from the other boys even more. He is also not game enough to attempt to play sport with the other boys at lunch time or initiate any interaction unless its when he's having a hyper silly moment!... What can i do to help him make friends? what can i say? Im stuck and i can see it's starting to affect him.