How should I react when my friends tell me they smoke?

You should just act naturally. IF they told you they want a reaction but yoir reaction was also fine

As long as you don't be a fool and join them in smoking (which is BAD for you and you can get cancer) - then don't worry about it. If they want to be stupid and smoke, you can't stop them, but you can control what YOU do.

Acting cool to fit in is never goin to make you happy either will putting on a front or pretense tell them how you really feel either they will respect you for it and maybe not smoke around you or maybe not you have to make the choice what’s more important your health since second hand smoke is known to kill or saying you have friends? Are they real true friends who will stick by you if needed or just acquaintances? Pray over matter never let anyone make you feel uncomfortable.

It's not really your choice, they told you so you know them better and so they don't have to hide it. Leave it at that, it shouldn't make you uncomfortable. It doesn't mean you have to smoke.

If your friends smoke, they do. Why do you have to have some "reaction" about it?

Be non judgemental

THEY do not smoke.

The CIGARETTES smoke........they are just suckers.

A cigarette is a tube with a fire at one end and a fool at the other

i think you should definitely let them know how you feel. i personally am not a fan of smoking and i let my friends know that. but you could also just stay away from them when they do smoke and ignore it. its whatever you choose. just be safe and smart

You should tell their parents and tell them you will do so. Once they are addicted, they will spend thousands of dollars on cigarettes and then more on doctor bills.

Not sure why you feel the need to act.