Within 8 hours
Circulation improves and oxygen levels in the blood return to normal

Within 24 hours
Carbon monoxide is eliminated from the body

Within 3 to 9 months
Breathing problems show improvement with lung function increased by 5% to 10%

Within 5 years
Risk of heart attack falls to about half that of a smoker

Within 10 years
Risk of lung cancer falls to half that of a smoker

Within 10 years
Risk of heart attack similar to someone who has never smoked

Source : National Asthma and Respiratory Training Centre 1999