• 20 minutes after quitting blood pressure drops to a level close to that before the last cigarette, and the temperature of hands and feet increases to normal.
  
• 8 hours after quitting carbon monoxide level in the blood drops to normal.
  
• 24 hours after quitting the chance of heart attach decreases.
  
• 2 weeks to 3 months after quitting circulation improves and lung function increases up to 30 %.
  
• 1 to 9 months after quitting coughing, sinus congestion, fatigue, shortness of breath decrease, and cilia regain normal function in lungs, increasing ability to handle mucus, clean the lungs, and reduce infection.
  
• 1 year after quitting excess risk of coronary heart disease is half that of a smoker’s.
  
• 5-15 years after quitting stroke risk is reduced to that of a non-smoker’s.
  
• 10 years after quitting lung cancer death rate is about half that of a continuing smoker’s, and the risk of cancer of the mouth, throat, esophagus, bladder, kidneys, and pancreas decreases
  
• 5 years after quitting the risk of coronary heart disease is that of a nonsmoker’s.

excerpt from:
American Cancer Society