This will probably make people hate me to know this but I don't give a sh*t. In my opinion & experience smoking cigarets is harder to quit than drugs, drugs were way easier to quit than cigarets were (well I've never been an alcoholic though)

Well eternalsleep I know this about you and I'm with you all the way! If quiting drugs and quiting smoking makes people hate you then they can go to hell, at least you don't do those things any more.

Do hugs not drugs!

I've never used any of these three, but I think smoking's the hardest to quit.

im never smoking or using drugs but iv seen too may real thing (not TV) and i think smoking harder but yes i drink and yes im under aged well soo f**k you if you dont like it im not an alcoholic
(they go to meetings )

I would have to experience them all first. =S
But I believe that any addiction is extremely hard to quit. One of the main things that makes an addiction easier or harder to quit is the time you have been addicted to it.

I wouldn't know, never tried (and never going to try)

looking at them scientifically though, I'd say they're all very hard because they messes with the brain and the entire nervous system which is very crucial and serious

Can't really say because I've never tried smoking or taking drugs