Findings: Relative to smoking, 57.3% perceived EC and 63.4% NRT to be less harmful; 25.4% perceived EC to be less addictive; and 32.2% thought replacing smoking with EC reduced health harms a great deal. Participants were less likely to endorse these beliefs if they had never vaped, and participants who had inaccurate nicotine knowledge were less likely to endorse all these beliefs apart from the addictiveness of EC. The main concerns about EC were a lack of research (48.3%), regulation or quality control (37.8%) and harmfulness of chemicals (41.6%).

Conclusions: Large proportions of UK smokers and ex‐smokers overestimate the relative harmfulness of e‐cigarettes and nicotine replacement therapy compared with smoking; misattributing smoking harms to nicotine is associated with increased misperceptions.