The European Parliament in Strasbourg has voted on a raft of measures to help curb smoking but stopped short of introducing plain packaging for cigarettes and tobacco.
Legislators put new limits on advertising for electronic cigarettes but have so far rejected proposals for them to be regarded as medicinal products.
Menthol and other flavours will be banned, but there is to be no ban on packs of slim cigarettes.
Some campaigners had called for e-cigarettes to be subjected to the same regulation as nicotine replacement therapies, such as patches and gum.
E-cigarettes consist of a battery, a cartridge containing nicotine, a solution of propylene glycol or glycerine mixed with water, and an atomiser to turn the solution into a vapour.
While nicotine is the addictive substance that keeps smokers hooked, Cancer Research UK says it is the toxic cocktail of chemicals in tobacco smoke that kills half of all long-term smokers.
The lack of tobacco in e-cigarettes means they are "almost certainly" a much safer way of getting a nicotine hit than smoking cigarettes, it says.
Liberal Democrat MEP Chris Davies said after the vote: "E-cigs can be a game changer in the fight against smoking. Hundreds of former smokers have written to tell me they have helped them give up cigarettes when nothing else worked.
"They are successful because they are not medicines but products that smokers enjoy using as an alternative to cigarettes. We should not do anything that makes e-cigs harder to obtain than tobacco cigarettes."
Adrian Everett, chief executive of e-cigarette brand E-Lites, said: "This is a fantastic result for public health and the millions of smokers around Europe who are switching to e-cigarettes."
The Scottish Government has already announced plans to introduce plain packaging as part of its strategy to create a smoke-free country in 20 years.