Background: The aim of the study is to assess the results of the treatment of 737 consecutive patients with DCIS with particular attention to the character of recurrences, other neoplasms and causes of deaths. Methods: A retrospective analysis was carried out of 737 consecutive DCIS patients treated in one institution in the years 1996-2011. The percentage of failures, causes of death, cumulated recurrence risk, DFS, OS depending on the method of treatment (mastectomy, breast conserving treatment BCT, breast conserving surgery BCS), was calculated. Results: 66 recurrences (42% DCIS, 58% invasive) were reported: 61 recurrences in the breast, 5 outside the breast. The comparison of mammography images before the initial treatment and after local recurrence revealed the true recurrence in the breast in 48/61 (79%) of cases. The cumulated recurrence risk after 15-year observation, after mastectomy, BCT and BCS was 3.2%, 19.5% and 31.2 %, respectively (p < 0.001). 15-year DFS after mastectomy, BCT and BCS was 72%, 65% and 48%, respectively (p < 0.001). 15-year OS after mastectomy, BCT and BCS was 75%, 83% and 70%, respectively, p = 0.329. In the course of the whole observation period 124 other neoplastic lesions in 121 patients (16%) were reported including 58 (8%) contralateral breast cancers. Deaths due to DCIS progression were reported in 4 (0.5%) of patients. An overwhelming majority (74/86) of deaths was linked to the age of the patients or other diseases, including other neoplasms. Conclusions: The highest recurrence risk reported in patients after BCS was unacceptable and, moreover, it kept growing over the fifteen years of observation. 79% of recurrences in the treated breast were true recurrences. Local recurrences were effectively treated without influence on OS. The percentage of deaths due to DCIS was low.