It's understandable that you'd be concerned about your friends. They're doing something that could cause them serious physical harm, and you don't want them to mess up their long-term health by smoking cigarettes. Unfortunately, though, there's not much more you can do about it. You've told them that you don't like that they smoke, and that you're concerned about their well-being. Other than that, you're pretty much stuck. They will have to decide on their own that they want to quit. Maybe they'll notice all the negative ramifications of smoking: They'll start to cough, have a gross taste in their mouths; their skin might look nasty, and their breath will be stinky (not to mention their clothes). Or maybe they'll be broke from spending tons of cash on cigarettes. Whatever the reason, quitting will have to be completely up to them.

That doesn't mean you have to like it or let them smoke around you (which puts your health at risk), but at some point, people have to live their own lives and make their own stupid mistakes. Let your friends know you love them, and that you're not trying to judge them at all but that you know smoking is bad for you and you don't want to see them get sick. You could even offer to help them in any way if they decide they need some help quitting. After that, it's out of your hands.

—Andrea Pyros