Electronic cigarettes appear to be at least as effective as nicotine patches in helping people to give up smoking, research suggests.
The devices, which are rapidly growing in popularity, produce a vapour containing nicotine.
The findings, presented at the European Respiratory Society, showed similar numbers quitting with e-cigarettes as patches, but more had cut down.
There was a call, however, for long-term data on safety.
As well as giving a nicotine hit, the e-cigarettes also mimic the sensory sensations of smoking. This has led to speculation that they may be a useful tool for people trying to quit.
A team at the University of Auckland, in New Zealand, conducted the first clinical trial comparing the devices with nicotine patches in 657 people.
The results published in the Lancet showed 7.3% using e-cigarettes had quit after six months compared with 5.8% using patches. However, the study did not involve enough people to definitively prove which is the better option.
After six months, however, the 57% of e-cigarette users had halved the number of cigarettes smoked each day compared with 41% in those using patches.
Prof Chris Bullen, from the University of Auckland, said: "While our results don't show any clear-cut differences between e-cigarettes and patches in terms of 'quit success' after six months, it certainly seems that e-cigarettes were more effective in helping smokers who didn't quit to cut down.
"It's also interesting that the people who took part in our study seemed to be much more enthusiastic about e-cigarettes than patches.
"Given the increasing popularity of these devices in many countries, and the accompanying regulatory uncertainty and inconsistency, larger, longer-term trials are urgently needed to establish whether these devices might be able to fulfil their potential as effective and popular smoking cessation aids."
Regulations around the world are catching up with the surge in the popularity of e-cigarettes. The EU and the UK are both working towards regulating e-cigarettes in the same way as medicines.
The products also divide opinion with some arguing they normalise smoking and others saying they may help people to give up.
Prof Peter Hajek, the director of the Tobacco Dependence Research Unit at Queen Mary University of London, described the study as "pioneering".
"The key message is that in the context of minimum support, e-cigarettes are at least as effective as nicotine patches.
"E-cigarettes are also more attractive than patches to many smokers, and can be accessed in most countries without the restrictions around medicines that apply to nicotine replacement therapy or the costly involvement of health professionals.
"These advantages suggest that e-cigarettes have the potential to increase rates of smoking cessation and reduce costs to quitters and to health services."
However, he did call for longer-term studies into the consequences of using the devices.
You can hear more from Prof Chris Bullen on Discovery on the BBC World Service.