"Many people hold mistaken beliefs about what causes cancer, tending to inflate the threat from environmental factors that have relatively little impact while minimising the hazards of behaviour," the International Union Against Cancer (UICC) said in a statement.
The study was released on the first day of the UICC's World Cancer Congress in Geneva, and was based on interviews with 29,925 people in 29 countries over the past year carried out by Roy Morgan Research and Gallup International.
It found that in high-income countries like the United States, Britain and Spain, 59 percent of people thought not eating enough fruit and vegetables was a cancer risk, while only 51 percent viewed alcohol intake in the same way.
"The scientific evidence for the protective effect of fruit and vegetables is weaker than the evidence that alcohol intake is harmful," the UICC said.
Moreover, 42 percent of people questioned in high-income countries said that drinking alcohol does not increase the risk of causing cancer -- a claim not borne out by statistics, according to the UICC.
"In fact, cancer risk rises as alcohol intake increases," it said.
In low- and middle-income countries, many people still adopt a fatalistic approach to the disease, with 48 percent of respondents saying they believed "not much can be done" to treat the illness -- against just 17 percent in high-income countries.
"Such a misbelief is worrying because it might deter people from participating in cancer screening programmes, which are important for saving lives," the UICC warned.
"In general, people in all countries are more ready to accept that things outside of their control might cause cancer (such as air pollution), than things that are within their control," such as being overweight, it added.
UICC President-elect David Hill said the survey showed "some big unheard messages".
"We know that people need to be given a reason why they should change. They need to be shown how to change; they need to be given resources or support to change; they need to remember to change," he said.
Cancer is the second leading cause of death worldwide, killing close to eight million people each year -- more than malaria, AIDS and TB combined, the UICC noted.
By 2030, this will increase to almost 16 million cases and around 11.5 million deaths per year, if current trends continue, it said.
World Health Organisation Director-General Margaret Chan told the opening of the Congress that "the time is right to make cancer control a development priority."
Cancer is no longer an "affluent" disease but affects millions of people in poor and developing countries whose infrastructure struggles to cope with the impact of the disease, she warned.
"Developing countries are now face-to-face with problems that affluent countries confronted decades ago ... but with the shift in the cancer burden, a nation's resource level can no longer be viewed as a barrier to cancer control," she urged.