Although electronic cigarettes (ECs) could reduce the harm caused by smoking, they may also present risks. While smokers would benefit if they replaced smoked tobacco with ECs, many continue smoking and remain at risk of serious harm. Other risks include experimentation among non-smokers, which may lead to nicotine addiction, and unknown long term effects of EC use. Because EC promotions emphasise potential benefits without explaining risks, users are likely to have an incomplete understanding of ECs’ risks and benefits. We will examine how smokers, and susceptible non-smokers’ perceive and use ECs, and then develop and test information messages that communicate ECs’ potential risks and benefits. We will assess the impact these messages have relative to other product attributes. Our findings will promote more informed user decisions, support proportionate policies that minimise trial and uptake among non-smokers, and balance the potential benefits ECs may deliver against the risks they might pose.