Many Christians treat smoking as one of the worst sins, something you can assume someone isn't a Christian if you see them doing. Tim Challies has a good post showing why such an attitude is Pharisaical.
Now I think a good argument can be made that smoking is morally wrong, even without the Bible, though it would be based on controversial ethical views that aren't common to all the main ethical theories. A virtue- or character-based ethic will have the easiest time showing this, I think, though other principles might count. Still, the other sorts of things that come out immoral on these grounds wouldn't compare too well with the Pharisaical people who place smoking on such a pedestal of evils. One consideration against smoking, that it pollutes, counts similarly against failing to recycle or driving an SUV. Another, the annoyance factor, counts just as much against mowing your lawn at 9am in a university area or playing loud music after 10pm in a neighborhood with kids. Pursuing the character trait of taking care of your body means avoiding sloth and gluttony as much as smoking, and those aren't on the list of total evils of most of the people I have in mind (though I'd say the same thing about someone who is overweight, whose spiritual level I have seen people wonder about). The second-hand smoke issue is stronger, but that depends on the context of the smoking, which can be controlled, and this reason also counts against people who have cars that pollute so badly as to harm people's health. Would most of these things be on the list of sins the observance of which should create the impression that someone probably isn't a Christian? Then neither should smoking.