Graphic images on the front of cigarette packaging do not put off young smokers, new research has suggested.
The images of diseased lungs and heart surgery have been on the front of packets since 2008.
But a study of 2,800 11 to 16 year-olds found that the images did not deter smokers.
However, the photos affected non-smokers and experimental smokers.
Published in the Tobacco Control journal, the Stirling University Study looked at data from before and after the images were introduced.
Around 10% of the children questioned were smokers, while the others were either non-smokers or children who had just experimented with smoking.
Although the number of young people who thought the warnings were capable of putting them off increased after the introduction of the images among both non-smokers and experimenters, the number of smokers who were put off remained almost constant – increasing from 13% to only 14%.
Lead researcher Dr Crawford Moodie said that while it was disappointing that the images did not seem to have an impact on smokers, the rise in the numbers of non-smokers and experimenters being deterred was a "really positive" result.
But he said there was also a risk of people becoming desensitised - the images and text warnings have not changed since they were introduced in 2003 and 2008 respectively.
He told the BBC: "Other countries regularly change their warnings. I think if we rotated them here they would have more impact."