More than four in 10 cancers – 600,000 in the UK alone – could be prevented if people led healthier lives, say experts.
Latest figures from Cancer Research UK show smoking is the biggest avoidable risk factor, followed by unhealthy diets.
The charity is urging people to consider their health when making New Year resolutions.
Limiting alcohol intake and doing regular exercise is also good advice.
According to the figures spanning five years from 2007 to 2011, more than 300,000 cases of cancer recorded were linked to smoking.
Key risk factors
A further 145,000 were linked to unhealthy diets containing too much processed food.
Obesity contributed to 88,000 cases and alcohol to 62,200.
Sun damage to the skin and physical inactivity were also contributing factors.