When does he smoke? Smoking can be fun, but in moderation. Once or twice a month, and at most once a week during social things is definitely not a problem.
When people start to smoke more and more, until its eventually daily.. things are going wrong in their life. It might be they have no goals, no interests or they might be depressed. A fair number of the people I know that slowly worked themselves up into daily smokers eventually started turning to harder stuff as well. First is usually "shrooms" or LSD. Neither are near as bad as their reputations, but its the beginning. ecstasy often follows until they become bold enough to try a "real" drug such as cocaine. And this is not coming from the ignorant masses. I used to smoke quite alot. I have a $160 bubbler that I still keep around for memories. After I stopped (and I don't mean for two weeks) everything began to improve in my life.
Again, I really hate to be cliche. The change might take weeks, months, or even over a year.. but it happens. You don't want to be tied down with somebody like that anyhow, even if they don't go overboard. Find somebody you can love AND be proud of.