Many pro-smoking videos on YouTube reach view counts in the hundreds of thousands and more. Yet, there is limited information on who is viewing these potentially misleading videos. Based on literature that suggests that positive portrayals of cigarette smoking are prevalent on YouTube and the fact that adolescents, who are the main users of YouTube, can be easily impacted by such misleading depictions, this dissertation focuses on furthering our understanding of pro-smoking videos, using youth (ages 15-21) with varying levels of interest in smoking as main subjects. Specifically, this dissertation is aimed at identifying the viewership and potential impact of smoking promotion YouTube videos. In an attempt to answer the question of who is viewing these videos, Study 1 was a selective exposure experiment that examined browsing patterns of youth who were given a choice set of 16 videos (eight smoking and eight non-smoking). Behavioral data revealed that youth with high interest in smoking were more likely to select and spend more time watching pro-smoking videos than were youth with lower interest in smoking. A secondary finding was that when given the impression that smoking videos were popular by manipulating view count, youth held more positive attitudes toward smoking. Study 2 examined post-exposure data collected as part of the selective exposure study. Correlational results showed that there was a significant positive association between selection of pro-smoking videos and smoking-related outcomes such as norms and attitudes. Youth with high interest in smoking also had more positive reactions to pro-smoking videos compared with their less interested counterparts. To establish directionality of the relationship between exposure and persuasion, Study 3 examined whether there were any direct effects of exposure to pro-smoking videos on smoking-related outcomes for youth interested in smoking. Contrary to expectations, there was no evidence that exposure to pro-smoking videos negatively impacted smoking-related outcomes. Therefore, an intervention to correct or inoculate against pro-smoking videos was not necessary, negating the need for a correctives study that had originally been proposed as part of this dissertation. Possible explanations for the findings are discussed along with implications and future directions for research.