I don't like my boyfriend because he smokes but he really like me and I kind of like him but my parents don't like him because he smokes and they think he stupid. I like him when we hang out with each other but when there are other people around he's different but when other people are not around and it just him and me it OK.

... then... break up with him?

I don't see the problem here.

From every guy that I have ever known of if they treat you different when others are around than alone you can NOT trust them. They end up being one extreme or another--
1. They treat their friends as more important and they treat you inconsiderate and you will find out they really end up having little respect for girls in general.
2. They treat you great around other people and crappy when you are alone--they are only trying to impress their friends that they have it all together and are better off than they are. In the long run you are only a prop in their scheme of what and where they want to be.

Find somebody that is for real with you.

I agree with n0help4u... but in my case:

My ex and I were very platonic among friends... mainly because we were both very against pda (public displays of affection)... so we actually just acted like two best friends when around other people, and were very affectionate when we were together alone.

I believe other people appreciated this and they even referred us as "the couple they feel comfortable around"

I don't like the man who smokes! But my friends keep telling me there is almost no man who does not smoke,so I begin to think maybe that's one of the reason that I still can't find a boyfriend even now! I am really confused for that! I don't like man who smokes at all!

... actually, I'm not so sure that's true.

... I don't smoke. Most of my friends don't smoke.