At 20 minutes after quitting:
- Blood pressure decreases
- Pulse rate drops
- Body temperature of hands and feet increases.
At 8 hours:
- Carbon monoxide level in blood drops to normal
- Oxygen level in blood increases to normal
At 24 hours:
- Chance of a heart attack decreases
At 48 hours:
- nerve endings begin regrowth
- ability to smell and taste improves
Between 2 weeks and 3 months:
- Circulation improves
- Walking becomes easier
- Lung function increases
Between 1 to 9 months smoke-free:
Starting as early as a month after you quit smoking, and continuing for the next several months, you may notice significant improvements in these areas:
- coughing
- sinus congestion fatigue
- shortness of breath
At One Year Smoke-Free:
- Your excess risk of coronary heart disease is decreased to half that of a smoker after one year
At 5 years smoke-free:
- from 5 to 15 years after quitting tobacco, stroke risk is reduced to that of people who have never smoked.
At 10 years smoke-free:
- risk of lung cancer drops to as little as one-half that of continuing smokers
- risk of cancer of the mouth, throat, esophagus, bladder, kidney, and pancreas decreases
- risk of ulcers decreases
At 15 years smoke-free:
- risk of coronary heart disease is now similar to that of people who have never smoked
From: http://quitsmoking.about.com/cs/afterquitting/a/after_quitting.htm