Health-related quality of life (QOL) is a multi-dimensional construct depending on clinical, socio-economical and psychological factors. QOL has been assessed as an outcome measure in the evaluation of different treatment alternatives. The objective of our study was to identify socio-economic and clinical determinants of quality of life among breast cancer survivors one year after diagnosis in a population based setting. We assessed QOL one year after diagnosis in a population based cohort of 387 women with breast cancer from Saarland (Germany) using the EORTC-QL-C30 questionnaire and the breast cancer specific module BR-23. The distribution of functional and symptom QOL-scores according to age, living conditions, employment status, comorbidity, tumor stage and therapy was compared with analysis of variance (ANOVA). Age, tumor stage and comorbidity were identified as most prominent determinants of QOL. Physical functioning and global QOL declined with older age, whereas older women with breast cancer reported better emotional and social functioning than younger patients. Similarly, older women were less concerned about body image and future perspective. Although global quality of life did not differ between women who underwent mastectomy compared with women after breast conserving therapy (BCT), women with BCT were less distressed by the body image but reported more breast related symptoms. In addition to tumor stage and mode of therapy, other non tumor-related factors, such as age and comorbidity have an important impact on the quality of life of breast cancer survivors.