Cancer survivors have a high risk of getting the disease again if they smoke cigarettes.
Researchers surveyed thousands of people with cancer about nine years after they were diagnosed.
Nearly 10% of those survivors admitted to smoking. A majority of them even smoke everyday, according to the survey.
Researchers found survivors were more likely to smoke if they were younger, less educated, or consumed more booze.
Experts say more interventions are needed for survivors who are unable to quit, since smoking can cause additional cancers.