Hi Trish.
Thanks for your question regarding surgery and smoking.
It really depends on what operation you are having. As the majority of plastic surgery procedures are elective and not life-threatening, it is preferable that we try to optimise your body's recovery and healing ability as best we can before, during, and after the surgery. Smoking has a very detrimental effect on circulation, and especially the microcirculation that is so important in keeping skin alive and wounds healed. 
I always advise my patients to at least try to reduce the amount of smoking in most cases. There are some higher risk procedures where I will not operate if the patient still smokes. This is in the best interest of the patient, both in regard to getting the best result as well as their safety.
All the very best.
Ray GohValley Plastic Surgery