Background: Few studies have prospectively assessed the impact of breast cancer (BC) on women's sexual lives. Therefore, this study examines the determinants of quality of sexual life (QOSL), sexual functioning (SF), and sexual enjoyment (SE) at 6 and 12 months after surgical treatment. Methods: All participants completed a measure of QOSL (The World Health Organization Quality of Life assessment instrument-100 (WHOQOL-100)-facet Sexual Activity) before diagnosis (Time-1), and 1 (Time-2), 3 (Time-3), 6 (Time-4) and 12 months (Time-5) after surgical treatment. At Time-1, women also completed questionnaires on personality (The State Trait Anxiety Inventory-trait, NEO-FFI), body image and self-esteem (WHOQOL-100), depressive symptoms (Center for Epidemiological Studies-Depression Scale), and fatigue (Fatigue Assessment Scale). Furthermore, SF and SE (The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Breast Cancer module) were measured from Time-2 onwards. Results: At baseline, the analysis included 223 women with early stage BC. Clinical factors did not predict QOSL, SF or SE. In the final analyses, trait anxiety predicted QOSL and SF at Time-4 (p's<0.01). At Time-5, agreeableness predicted QOSL and SE (p's<0.05). Having a partner and age predicted SF, while SE was predicted by educational level (Time-4). In addition, fatigue predicted SE at Time-4 (p<0.05). In general, QOSL diminished across time, while SF improved. However, women with a mastectomy did not differ from women with breast conserving therapy. Conclusions: Mainly personality and psychological factors affect patients' sexuality after surgical treatment. Clinical factors did not predict QOSL, SF or SE. More knowledge in this field will help professionals to identify women who are at risk of experiencing sexual problems and consequently will contribute to provide adequate support. Copyright © 2009 John Wiley & Sons, Ltd.