Abstract: The purpose of the study was to review the treatment outcomes of 198 patients treated with breast-conserving surgery (BCS) and whole breast radiation therapy using lung density correction for ductal carcinoma in situ (DCIS). Between April 1985 and December 2002, 198 patients with 200 lesions diagnosed as DCIS (AJCC stage 0) were treated at the University of Michigan. All underwent BCS and whole breast radiotherapy. Median total follow-up was 6.2 years (range: 0.8–18.2). The 5- and 10-year cumulative rates of in-breast only failure were 5.9% (95% CI: 2.6–9.3%) and 9.8% (95% CI: 5.2–14.4%), respectively. Factors that significantly predicted for an increased risk of local failure were family history of breast cancer, positive or close surgical margins and age ≤ 50 years at diagnosis. Cosmetic outcome was scored as “excellent” or “good” in 94% of the assessed patients. On multivariate analysis, only patient separation significantly predicted cosmetic outcome (p = 0.04). BCS and radiotherapy using lung density correction resulted in high rates of local control at 5 and 10 years with excellent cosmetic results. To the best of our knowledge, this is the first study to report outcome in a series of patients with DCIS treated with lung density correction and results compare favorably with other series in which plans were calculated using unit density.