Reducing exposure to environmental tobacco smoke significantly reduces lung cancer risk. We used family communication patterns theory and the theory of planned behavior to examine whether perceived norms and lung cancer worry more strongly influenced intentions to avoid environmental tobacco smoke in families higher in conformity and conversation orientations. Results from 52 individuals in 17 high-risk lung cancer families showed injunctive norms were positively related to intentions when families conformed and conversed more. Lung cancer worry was positively related to intentions in high conformity families and negatively related to intentions in low conformity families. Findings can benefit interventions to reduce environmental tobacco smoke exposure.