Since when did Darth Vader start smoking? He never smoked in Star wars before.  Maybe he got stressed out from the rebel alliance messing with him or maybe he's been feeling guilty from all those little jedi children he killed before he turned to the dark side.  Man, that was seriously messed up.  Just like, "Ok, kiddes, close your eyes, I have a suprise for you!" And then they reply, "Oh really Anakin Skywalker? It must be some suprise because you can do some amazing things with the force!"  Then, instead, he just kills all these kids. Damn... Not cool Anakin. I mean think about it, seriously, you're going to be a dad soon, with responsibilities.  Darth, you can't just go around slashing children! And the force is not going to be able to help you raise those kids!  So yeah... That's probably the reason he started smoking. Most people would need a cigarette after what he's been though.. Or wait, maybe this is the cigarette he had after making sweet sweet love to Natalie Portman?  Anyway, it's good thing he has that light saber.