Hostility is a multifaceted construct encompassing affective, behavioral, and cognitive aspects. There is preliminary evidence linking hostility to poorer outcomes in smoking cessation treatment; however, it is unclear which components of hostility are most important in cessation. In this study, the authors examined multiple aspects of trait hostility in 92 heavy social drinkers who were seeking smoking cessation treatment. Consistent with their hypothesis, the authors found that the cognitive component of hostility was most relevant to smoking cessation outcome. Specifically, those who expressed bitterness about their lives and tended to believe that they had poor luck and had gotten a raw deal out of life had poor smoking cessation outcomes. Cognitive measures of hostility also predicted greater nicotine withdrawal symptoms 1 week after quitting smoking. Other components of hostility including anger and both physical and verbal aggression did not significantly predict smoking outcome or nicotine withdrawal. Further examination of how a hostile worldview contributes to smoking cessation failure is warranted, as this facet of hostility may prove a valuable target for smoking cessation interventions. (PsycINFO Database Record (c) 2009 APA, all rights reserved).