There are many conflicting results in the literature comparing quality of life following breast-conserving therapy (BCT) and mastectomy. This study compared long-term quality of life between breast cancer patients treated by BCT or mastectomy in three age groups. Patients (n = 990) completed a quality of life survey, including the European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire (EORTC QLQ-C30), at regular intervals over 5 years. In the cross-sectional data, mastectomy patients had significantly (p < 0.01) lower body image, role, and sexual functioning scores and their lives were more disrupted than BCT patients. Emotional and social functioning and financial and future health worries were significantly (p < 0.01) worse for younger patients. There were no differences in body image and lifestyle scores between age groups. There was also no interaction between age and surgery method. Even patients > or =70 years of age reported higher body image and lifestyle scores when treated with BCT. The repeated measures analysis indicated that four functioning scores, half the symptom scores, future health, and global quality of life improved significantly (p < 0.01) over time. All these variables increased significantly for BCT patients and those 50 to 69 years of age. Body image, sexual functioning, and lifestyle disruption scores did not improve over time. BCT should be encouraged in all age groups. Coping with appearance change should be addressed in patient interventions.