When developing messages for a communication intervention targeting behavior change, the interventionist must decide which messaging topics are most worthwhile to target. This dissertation focuses on the role of misinformation beliefs in such interventions, and whether such beliefs merit campaign focus. Using a longitudinal nationally representative survey, Study 1 tested the hypothesis that behavior-specific beliefs regarding COVID-19 vaccination would account for any observed relationship between coronavirus misinformation beliefs (misinformation beliefs that are not specific to the anticipated consequences of COVID-19 vaccination) and subsequent vaccine uptake. Contrary to our hypothesis, Study 1 found a residual observed relationship between coronavirus misinformation beliefs and subsequent vaccine uptake even after adjusting for baseline behavioral beliefs. Intriguingly, post-hoc exploratory analyses show that (a) after also adjusting for follow-up behavioral beliefs, this association was no longer significant, and (b) that coronavirus misinformation beliefs predicted significantly less positive change in behavioral beliefs over time. Using two new behavioral focuses, Study 2 provides further evidence that coronavirus misinformation beliefs constrain positive change in behavioral beliefs. Building on Studies 1 and 2, Study 3 uses confirmatory factor analyses alongside additional evaluations of construct validity to distinguish beliefs that are specific to two behaviors of interest from misinformation and conspiracy theory beliefs that are relevant to, but are not explicitly specific to, these behaviors. Finally, Study 4 provides experimental evidence that such topic-related conspiracy theory and general misinformation beliefs do not constrain responsiveness to messages targeting promising behavioral beliefs. Informed by the pattern of findings across these four studies, I argue that campaign planners may not want to spend their limited resources and opportunities for messaging exposure targeting and/or correcting general misinformation within a behavioral domain. Rather, in line with the Reasoned Action Approach and prior work, campaign planners promoting health and environmental behaviors may want to focus their attention and resources on targeting promising behavior-specific beliefs about the expected outcomes of engaging in a behavior of interest.