The purpose of the present study was twofold: first, to describe changes of Health-Related Quality of Life (HRQoL) during the adjuvant treatment among postmenopausal women with breast cancer; second, in the same population to identify the best predictors of Overall Quality of Life (QoL) after treatment, from perceived functioning, symptoms, emotional distress and clinical/demographic variables measured at baseline. The study group was 150 women (> or = 55 years of age) scheduled for adjuvant chemotherapy (CT, n=75) or radiotherapy (RT, n=75). They were examined before (baseline), during and after completing the treatment. Data about QoL, perceived functioning, symptoms and emotional distress were collected with the European Organisation for Research and Treatment of Cancer (EORTC)-QLQ-C30, BR23 and Hospital Anxiety and Depression Scale (HADS) questionnaires. The general finding was that the adjuvant treatments were associated with decrease in overall QoL, physical and role functioning, anxiety and body image, as well as with increase in fatigue, dyspnoea, pain, nausea/vomiting, constipation and systemic therapy side effects measured over time. For women receiving CT, better emotional functioning and less pain at baseline predicted better overall QoL at the end of the treatment. For women receiving RT, better physical and emotional functioning, less breast symptoms and lower tumour stage at baseline predicted better overall QoL at the end of the treatment.