ABSTRACT Use of nicotine and tobacco products (NTPs) among youth is a persistent public health problem in the United States. Initiation of NTPs in adolescence is associated with increased frequency of use, adverse impacts on brain development, nicotine addiction, and increased risk of cancer. Major factors associated with NTP use include youth-targeted marketing and media advertisements for these products; this is particularly true for Black, Hispanic, and sexual and gender minority (SGM) youth. These youth are intentionally targeted with messaging by nicotine and tobacco companies through carefully curated media advertisements and marketing meant to build trust and recruit new users. With the proliferation of social media, this is more pervasive as these youth are now exposed to messaging from both tobacco company marketing and self-generated content from social media users. However, it is not well known how these youth are exposed to NTP-related misinformation on social media and how these exposures are associated with susceptibility to NTP initiation. Therefore, the goal of this proposal is to first identify NTP-related misinformation on a variety of youth-oriented social media platforms and then assess associations between misinformation exposure and susceptibility to NTP initiation among youth, particularly youth who identify as Black, Hispanic, and/or SGM. Informed by these results, we will develop health communication messages to counteract misinformation and assess their acceptability to youth. Core to this proposal is the use of a Youth Participatory Action Research approach via the development of a Youth Collaborative (n=20). Comprised of an inclusive group of youth ages 13-17, the Youth Collaborative will play an integral role in completing the following specific aims: (1) classify the most pervasive and salient NTP-related misinformation on youth-oriented social media platforms via human- centered design (HCD) activities, social media data collection, qualitative and automated data analysis processes, and social network analysis; (2) assess social media-based exposure to NTP-related misinformation and associations with susceptibility via a cross-sectional survey of with 700 youth ages 13-17 with oversampling of Black, Hispanic, and SGM youth; and (3) develop health communication messages using HCD activities and assess the acceptability of these messages with a subsample of youth from Aim 2 who are susceptible to NTP initiation. Our interdisciplinary team has collaborated for over a decade to examine youth attitudes and behaviors related to nicotine and tobacco products, social media use, engagement with media, and community-based participatory research. We will leverage this knowledge and experience to complete these aims, the results of which can be used to develop scalable interventions that can counteract targeted misinformation and prevent NTP initiation among Black, Hispanic, and SGM youth and ultimately eliminate disparities in...