A health expert wants the Ministry of Health to fill the gap in advertising regulations for e-cigarettes.

Cosmic Corner has a billboard advertising e-cigarettes and start up kits on Christchurch's Moorhouse Avenue, only a few hundred metres away from a high school.

Start up kits are being advertised from $29.95 and Cosmic Corner is currently well within its legal rights to do this.

Professor of Public Health Nick Wilson says there's a gap in our laws for this relatively new product.

He said ideally, advertising regulations should be changed so they mirror regulations for normal cigarettes, and said the ministry should investigate whether they could be used as a potential way of quitting for those already smoking.

Mr Wilson said very little is known at this stage the harm e-cigarettes could cause.

"There is some concern about particular flavours that could do harm to the lungs but also we don't really know how risky it [would be] if these are available on the market in terms of young people taking them up."

Mr Wilson said although e-cigarettes are still a small part of the market, but they're growing in popularity.