This really should be a no brainer. Basically, if you smoke then PLEASE STOP!
Smoking will not only kill you a lot faster but will impede your weight loss efforts.
A study conducted by the university of Alberta concluded that women who stopped smoking and kept exactly the same eating habits shed on average a staggering 30% of their body mass. The probably cause they concluded was that people who smoke also tend to frequent bars and restaurants where mindless eating and drinking happens.