Ductal carcinoma in situ (DCIS) has an excellent prognosis, but its management can resemble that of early invasive breast cancer. We compared aspects of quality of life of women with DCIS to that of women with invasive disease during the first year after treatment initiation. Participants came from consecutive series of women with newly diagnosed, non-metastatic breast cancer treated in eight Quebec hospitals in 2003. Psychological distress and health-related quality of life were measured using the Psychiatric Symptom Index (PSI) and the SF-12 mental and physical component scales (MCS, PCS). Data were obtained 1, 6, and 12 months after the start of treatment. We used generalized linear models to compare mean scores and explored the possible clinical significance of between-group differences with effect size (ES). Participation and retention among eligible women were high, 86 and 97%, respectively. Among the 800 women who completed all interviews, 13.4% (n = 107) had DCIS and 86.6% (693) invasive disease. No statistically significant between-group differences were found at 1, 6, or 12 months in psychological state (PSI and MCS: P values from 0.065 to 0.904; ES from -0.01 to -0.21). Women with DCIS reported significantly higher levels of physical health, particularly when compared at 1 month to women with invasive disease who had chemotherapy (P value < 0.0001; ES = 0.82). Measured in symptoms of psychological distress, the better prognosis or less aggressive management of DCIS does not offset the general psychological effects of a cancer diagnosis to any great degree.