More than half of smokers do not appreciate the risks associated with the habit, the NHS has said.
The research from NHS Smokefree revealed that 53% of smokers underestimate the number of annual deaths from smoking-related diseases by at least 70,000.
The actual number of such deaths is more than 80,000.
A further 58% underestimated how many long-term smokers die early from smoking-related diseases.
According to the NHS, the figure is one in two of all such smokers. Of those surveyed, 8% did not realise smoking can seriously damage their health or lead to early death.
The Government is urging people to quit the habit as a New Year's resolution.
Public Health Minister Anne Milton said: "Quitting smoking is the very best thing you can do to improve your health this New Year.
"What's clear is that the majority of smokers want to quit smoking and free NHS help is available to help them quit for good.
"The new and improved NHS Quit Kit is available in chemists who are working with us across England and will give smokers who want to give up advice, information and tools to help them enjoy a healthier 2012."
Smokers also underestimated how much money goes on cigarettes. Someone smoking 20 cigarettes a day spends on average £2,405 a year on the habit, but smokers believed it cost roughly £1,800.