PURPOSE: Women diagnosed with ductal carcinoma in situ (DCIS) often experience adverse changes in health-related behaviors following diagnosis. The impact of health behaviors on long-term quality of life (QoL) in DCIS survivors has not been investigated. METHODS: We examined the association of post-diagnosis body mass index (BMI), physical activity, alcohol, and smoking with QoL among 1448 DCIS survivors aged 20-74 enrolled in the population-based Wisconsin in situ Cohort from 1997 to 2006. Health behaviors and QoL were self-reported during biennial post-diagnosis interviews. Physical and mental QoL were measured using the validated SF-36 questionnaire. Generalized linear regression was used to determine the association between behaviors and QoL with adjustment for confounders. Lagged behavior variables were used to predict QoL during follow-up and avoid reverse causation. RESULTS: Women reported 3,536 QoL observations over an average 7.9 years of follow-up. Women maintaining a healthy BMI had on average a significantly higher summary measure score of physical QoL than obese women (normal versus obese: β = 3.02; 2.18, 3.85). Physical QoL scores were also elevated among those who were physically active (5 + h/week vs. none: β = 1.96; 0.72, 3.20), those consuming at least seven drinks/week of alcohol (vs. none; β = 1.40; 0.39, 2.41), and nonsmokers (vs. current smokers: β = 1.80; 0.89, 2.71). Summary measures of mental QoL were significantly higher among women who were moderately physically active (up to 2 h/week vs. none: β = 1.11; 0.30, 1.92) and nonsmokers (vs. current smokers: β = 1.49;0.45, 2.53). CONCLUSIONS: Our results demonstrate that maintaining healthy behaviors following DCIS treatment is associated with modest improvements in long-term QoL. These results inform interventions aimed at promoting healthy behaviors and optimizing QoL in DCIS survivors.