Background <p>Tobacco marketing shapes consumer perceptions, particularly among young people. Despite regulatory restrictions, subtle tactics may continue to mislead youth and young adults. This study examines how specific features in cigarette and e-cigarette ads affect perceived harm and addictiveness among 18-20-year-olds.</p> Methods <p>We recruited 1,708 U.S. participants aged 18–20 across two survey waves (2022–2023). Participants viewed randomized cigarette and e-cigarette ads and rated perceived harm and addictiveness. Ads (<i>n</i> = 221) were coded for youth-relevant features. Mixed-effects logistic regression assessed associations between ad features and perceptions, adjusting for demographics, tobacco use, brand familiarity, and wave.</p> Results <p>For e-cigarette ads, flavors and gift promotions were associated with a lower likelihood of inaccurate harm perceptions, while sweepstakes, social media engagement, and socialization themes were linked to a higher likelihood of inaccurate harm perceptions. In cigarette ads, use cues and pleasure claims were linked to a lower likelihood of inaccurate harm perceptions, whereas gift promotions were linked to a higher likelihood of misperceptions. Regarding addiction, price promotions and use cues in e-cigarette ads were associated with a lower likelihood of inaccurate addiction perceptions, while sweepstakes, social media engagement, and socialization themes were linked to a higher likelihood of inaccurate addiction perceptions. For cigarette ads, only use cues predicted a lower likelihood of inaccurate addiction perceptions.</p> Conclusion <p>Advertising features can influence young adults’ misperceptions of nicotine and tobacco product risks. Specifically, sweepstakes, social media engagement, and youth-oriented socialization themes may obscure harm and addictiveness, especially for e-cigarettes. Findings support comprehensive regulation to address misleading marketing.</p>