Exposure to health information from the public communication environment (PCE) can influence people’s perceptions of and behaviors relevant to public health issues. Communication scholars have explored factors that potentially moderate the effects of exposure to health information. Identity, a person’s answer to the question “Who am I?” at a given moment, is one of those potential moderators. That is, how people react to messages can substantially rely on how they define themselves when they are exposed to the messages. This dissertation addressed this topic in the context of tobacco regulation communication. It comprised four different studies. Study 1 was a foundational study which examined the relationship between the PCE about smoking/vaping and self-reported routine exposure (i.e., scanning) to smoking/vaping-relevant information. It analyzed the TCORS content data, which included millions of media items, and the TCORS survey data, collected among 10,642 U.S. youth and young adults that could represent the population. Study 2 conducted secondary analyses of the TCORS survey data to test the association between scanning and support for anti-smoking and anti-vaping policies. Study 3 was an extension of Study 2 in terms of assessing moderating effects of smoking and vaping statuses, proxies for smoker and vaper identities, using Study 2’s regression models. Study 4 aimed to test the moderating roles of smoker and vaper identities via a set of online survey experiments. It further examined whether numerical minority status was related to salience of the identities and whether effects were moderated by salience. Study 1 found that the relationship between the PCE and scanning was not significant. Regardless of this result, given other prior evidence supporting a significant association between the PCE and scanning, Study 2 and 3 kept scanning as the research variable. Evidence from Studies 2 to 4 suggested salience was negatively correlated to numerical minority status and sometimes significantly moderated exposure effects. However, evidence was not always stable both among smokers and vapers, specifically among vapers. Based on the evidence, this dissertation argued for the usefulness of adopting a theoretical framework of identity in communication studies and suggested the importance of investigating situational factors affecting salience of an identity.