Objective To assess adolescents’ baseline knowledge of smoking health harms scheduled to be covered in future graphic health warnings (GHWs) and inform the content of future tobacco control public communication campaigns.

Methods Cross-sectional survey of 8631 secondary school students (mean age=14.5 years) in Australia in 2022/2023 (weighted n=8655). Students were asked (a) for their agreement/disagreement that smoking causes each of nine harms (eg, lung cancer, stomach cancer and asthma), (b) to indicate where most of smoking’s harmful chemicals come from and (c) for their agreement/disagreement concerning the relative harmfulness of different tobacco product attributes (eg, menthol and roll-your-own). Multivariable logistic regression analyses examined associations between students’ knowledge and perceptions and their smoking status, controlling for demographics and school-level clustering.

Results Students had greater awareness of harms previously publicised in Australia. Among students who had never smoked, those open to future smoking had lower awareness of six smoking harms than those with a firm future intention not to smoke. Only 17.8% of all students were aware that most harmful chemicals came from burning the tobacco, with 37.8% not knowing and 34.6% attributing the source to additives. Three-quarters held misperceptions that roll-your-own cigarettes are less harmful than factory-made cigarettes or that cigarette smoke which feels light or smooth is less harmful than smoke that feels harsh. Only 25.9% of students were aware that menthol cigarettes are more addictive than non-menthol cigarettes.

Discussion New GHWs and public communication campaigns could improve student knowledge of previously unpublicised smoking harms and counter pervasive misperceptions about tobacco products.