Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: Problematic substance use in adolescence and emerging adulthood is a significant public health concern in the United States due to high recurrence of use rates and unmet treatment needs coupled with increased use. Consequently, there is a need for both improved service utilization and availability of recovery supports. Given the ubiquitous use of the Internet and social media via smartphones, a viable option is to design digital treatments and recovery support services to include Internet and social media platforms. Objective: While digital treatments delivered through social media and the Internet are a possibility, it is unclear how to tailor interventions using these tools for groups with problematic substance use. There is limited research comparing consumer trends of use of social media platforms, use of platform features, and vulnerability of exposure to drug cues online. The goal of this study was to compare digital platforms used among adolescents (Generation Zs) and emerging adults (Millennials) attending outpatient substance use treatment and to examine receptiveness to using these platforms to support substance use treatment and recovery. Methods: Generation Zs and Millennials enrolled in outpatient substance use treatment (n = 164) completed a survey examining social media use, digital intervention acceptability, frequency of substance exposure, and substance use experiences. Generation Zs (n = 77) completed the survey in July 2018. Millennials (n = 114) completed the survey in May 2016. Results: Generation Zs had an average age of 15.66 years (SD = 1.18) and primarily identified as male (50.9%). Millennials had an average age of 27.66 years (SD = 5.12) and also primarily identified as male (74.8%). Most participants owned a social media account (M: 82.0%, Z: 94.3%), and used it daily (M: 67.6%, Z: 79.2%); however, Generation Zs were more likely to use Instagram and Snapchat while Millennials were more likely to use Facebook. Further, Generation Zs were more likely to use the features within social media platforms (e.g., instant messaging M: 55.0%, Z: 79.2%, and watching videos (M: 56.8%, Z: 81.1%)). Many participants observed drug cues on social media (M: 76.4%, Z: 79.2%). However, fewer observed recovery information on social media (M: 30.6%, Z: 34.0%). Participants felt that social media (M:55.0%, Z: 48.1%), a cell phone application (M: 36.9%, Z: 45.3%), texting (M: 28.8%, Z: 45.3%), or a website (M:39.6%, Z: 32.1%) would be useful in delivering recovery support. Conclusions: Given the high rates of exposure to drug cues on social media, disseminating recovery supports within a social media platform may be the ideal just-in-time intervention necessary to decrease rates of recurrent use. However, our results suggest that cross-platform solutions capable of transcending generational preferences is necessary and one-size-fits-all digital interventions should be avoided.