OBJECTIVES: Although less than 5% of breast cancers occur among women under 45, the impact on health-related quality of life (HRQOL) may be significant since these cancers strike earlier in a woman’s life. This study addresses a gap in the literature on the health utility impacts of breast cancer among U.S. women ages 18-44. METHODS: Self-reported cancer history and HRQOL for US women were measured from the 2009 and 2010 Behavioral Risk Factor Surveillance System (BRFSS), a nationally representative population-based survey. BRFSS did not include preference-based measures of HRQOL, so Jia et al.’s (2011) mapping of Healthy Days (HRQOL-4) to the EQ-5D and Shaw et al.’s (2005) estimates of US utility weights were applied. The difference in health utilities and in Healthy Days (non-preference-weighted) was assessed using multivariate regression controlling for sociodemographics and major health risk factors. RESULTS: A total of 343 of 133,294 women ages 18-44 in the 2009-2010 BRFSS reported breast cancer. Unadjusted mean utility was .073 lower (p<0.01) among women with a history of breast cancer. Among women ages 45 and older, the difference was much smaller, 0.008 (p<0.01). Adjusting for sociodemographic factors and years since diagnosis, the decrease in health utility for breast cancer was 0.090 lower (p<0.01) for women 18-44; similar analysis of women ages 45 and older with breast cancer showed an estimated impact of 0.017 (p<0.01). Mean unhealthy days (physical, mental, or activity limitations) were also significantly lower in younger women with breast cancer. CONCLUSIONS: Although women 18-44 are a small fraction of breast cancer cases, the health utility impact at the individual level is substantial. Although the utility decrement is significant for women of all ages, the impact of breast cancer is 5-6 times greater in younger women. Age-specific utility values of breast cancer are critical for generating accurate results from cost-utility and modeling.