Electronic "e-cigarettes" can improve the success rate of people trying to quit smoking by 60% compared with nicotine patches and gum, or relying on will power alone, research has shown.
The findings follow a survey of 5,863 smokers in England who had attempted to stop smoking without the aid of prescription medication or professional support.
Of those using e-cigarettes, a fifth reported having quit "real" cigarettes at the time the study was carried out.
The research, published in the journal Addiction, suggests that e-cigarettes could play a positive role in reducing smoking rates, say experts.
Study leader Professor Robert West, from University College London, said: "E-cigarettes could substantially improve public health because of their widespread appeal and the huge health gains associated with stopping smoking.
"However, we should also recognise that the strongest evidence remains for use of the NHS stop-smoking services. These almost triple a smoker's odds of successfully quitting compared with going it alone or relying on over-the-counter products."
The same team, chiefly funded by Cancer Research UK, also found that most e-cigarette use involved first-generation 'cigalike' products rather than newer devices that use refillable cartridges and a wider choice of nicotine concentrations and flavours.
Co-author Dr Jamie Brown, also from University College London, said: "We will continue to monitor success rates in people using e-cigarettes to stop smoking to see whether there are improvements as the devices become more advanced."
Prof West acknowledged that some quitters may want to keep using e-cigarettes indefinitely, and it was not clear whether or not this carried long-term health risks.
But he added: "From what is known about the contents of the vapour these will be much less than from smoking.
" Some public health experts have expressed concern that widespread use of e-cigarettes could 're-normalise' smoking. However, we are tracking this very closely and see no evidence of it. Smoking rates in England are declining, quitting rates are increasing and regular e-cigarette use among never smokers is negligible."
Alison Cox, Cancer Research UK's head of tobacco policy, said: "Smoking is the largest preventable cause of cancer and accounts for more than one in four cancer deaths in the UK - so helping smokers to stop is a vital contribution to the health of the UK.
"E-cigarettes may have a role in helping people to quit smoking but while the rapid rise in their popularity suggests a real opportunity, the evidence for their effectiveness is so far limited. Cancer Research UK is funding much-needed research into e-cigarette use to help inform policy development and individuals' choices, and research such as this is helping to paint a clearer picture."