Smokers are increasingly turning to e-cigarettes to beat the habit, with the market "booming" by 340% over the past year to reach an estimated £193 million in 2013, according to analysts Mintel.
Meanwhile, products to help smokers quit, such as gum, tablets and patches, have seen growth slow from annual increases of 6% to 10% between 2009 and 2012, to 1.7% last year, to reach a value to £131m.
Mintel senior personal care analyst, Roshida Khanom, said: "Although e-cigarettes are largely marketed as an alternative to smoking, smokers have been using them to cut down or quit smoking.
"But with the growing popularity of e-cigarettes, there is concern that young people may take up 'vaping' as a less harmful alternative to smoking."
E-cigarettes provide a hit of nicotine - a highly addictive drug - and some fear they reinforce the behaviour of smoking, making it harder to give up in the long term.
Scottish Public Health Minister Michael Matheson said this week that the case for restricting the sale of e-cigarettes "make sense" and the practicalities of any such ban would be worked through.