Both smokers and overweight persons report frequent efforts to change their behavior. Long-term success, however, is achieved by few. Interventions are needed to improve long-term success in smoking cessation and weight loss. Our research program is designed to address this need and to test a novel conceptualization of health behavior change that is based on the premise that the initiation and the maintenance of behavior change involve different decision processes. Positive expectations about the consequences of behavior change are thought to guide decisions to initiate behavior change, whereas satisfaction with the outcomes afforded by one's behavior guides decisions about maintenance. In the first phase of our research program, we are evaluating the effect people's expectations about the benefits of behavior change have on immediate and long-term behavioral outcomes. Specifically, participants are assigned to either an 'optimistic' treatment condition that emphasizes positive expectations for outcomes or a 'balanced' treatment condition that gives equal weight to the benefits and costs associated with behavior change. The impact of manipulating people's expectations about behavior change will be examined in the areas of smoking cessation and weight loss. Results of these studies will advance research on health behavior change by informing practical and theoretical understanding of the factors that control decisions to initiate a new pattern of behavior and to maintain it.