Work it out or throw him to the curb?

We've been together for five months now and at the beginning of our relationship he asked me how I felt about him smoking and chewing. I told him chewing I find disgusting and i'd rather he didnt and smoking i wouldnt mind every now and then but not bad to the risk of his health. He promised that he wouldn't do either and said it was out the window. I was shocked. Anyway, five months down the road i've began to notice small little things like chewing tins, and lighters. I never asked him about it but he made up excuses that they were his friends. But just last night we were fighting and then he asked me if i "trust" him (he goes to college 2.5hrs away) Isn't that a bit hypocritical? So i came out with what I suspected with the tins and lighters. He came clean with it all that he has been chewing and smoking every once and awhile. He told me that he didn't want to tell me cause he thought id think less of him. But if he lied to me once and knew it would bother me, isnt it slim that he will change?