Objective To analyze the clinicopathological features and prognosis in patients with breast cancer treated with breast-conserving therapy according to the age when breast cancer diagnosed. Methods Clinical data of 827 patients with breast-conserving therapy in Tianjin Medical University Cancer Institute and Hospital from October 1997 to May 2010 were analyzed retrospectively. According to age when breast cancer was diagnosed, patients were subdivided into three groups. Clinicopathological characteristics and survival were compared between three groups. Results Of the 827 patients, 129 cases were ≤35 years old, 530 cases were 36-54 years old and 168 cases were aged ≥55 years. The proportion of lymph node metastasis number ≥4 and the negative rate of hormone receptors were higher in patients with age ≤35 years old. The 5-year local regional recurrence-free survival rates were 86.0%, 93.6%, and 94.0% for patients aged ≤ 35 years old, 36-54 years old, and ≥55 years old, respectively (P < 0.01). The 5-year distant metastasis-free survival rates were 88.4%, 91.3%, and 94.6% for patients with age ≤35 years old, 36-54 years old, and ≥55 years old, respectively (P > 0.05). The 5-year over⁃ all survival rates were 91.5%, 94.3%, and 95.2% for patients aged ≤35 years old, 36-54 years old, and ≥55 years old, respe tively (P > 0.05). Multivariate analysis showed that 5-year local regional relapse risks were significantly increased in patients aged ≤35 years compared to patients aged 36-54 years and ≥55 years (P < 0.05), and the 5-year distant metastasis risk was higher in this group than that of patients aged ≥55 years (P = 0.014), while 5-year mortality risk was not increased in patients with age ≤35 years old (P > 0.05). Conclusion After breast-conserving therapy, the risk of 5-year local regional recurrence and distant metastasis are relatively higher in patients aged ≤35 years old, while the risk of mortality within 5 years does not increase in this group. Patients with age ≤35 years old remain appropriate candidates for breast-conserving treatment. [ABSTRACT FROM AUTHOR]