Many people are unaware of the links between cancer and diet, body weight and physical activity, a charity said.
The World Cancer Research Fund said that many people do not know that there is a lot they can do to prevent cancer.
The charity said it is working to dispel the myth that all cancers are unavoidable.
A new WCRF poll, released to mark World Cancer Day, found that 49% of people do know know that diet can affect people's risk of getting cancer.
Two thirds of the 2,000 British adults polled did not know about the links between cancer and physical activity and 59% were unaware of the correlation between cancer and body weight.
And more than a third of people (34%) believe that the chances of getting cancer are mainly due to a family history of the disease even though only five to 10% of cancers are linked to inherited genes.
The charity is working alongside the Union for International Cancer Control (UICC) to encourage people to take steps to reduce the risk of developing cancer, including:
:: Eating a healthy diet with lots of vegetables, fruit, pulses and whole grains
:: Maintaining a healthy weight with a BMI between 18.5 and 25.
:: Bring physically active for at least 30 minutes every day.
WCRF general manager Amanda McLean said: "On World Cancer Day 2014 it's very alarming to see that such a large number of people don't know that there's a lot they can do to significantly reduce their risk of getting cancer.
"We would like all sectors of society - including the government, manufacturers, retailers and charities - to work together to raise cancer prevention awareness.
"In the UK, about a third of the most common cancers could be prevented through being a healthy weight, eating a healthy diet and being regularly physically active. These results show that many people still seem to mistakenly accept their chances of getting cancer as a throw of the dice. But by making lifestyle changes today, we can help prevent cancer tomorrow."