This study describes women's sexual functioning in the early weeks of breast cancer treatment and the possible sexual changes that women may experience compared with pre-treatment functioning. Seventy-five patients filled out a questionnaire on sexual functioning and participated in a semi-structured interview on changes in sexual life and intimacy after treatment. Sixty-two women were sexually active before treatment; three post-treatment patterns of sexual behaviour were identified: 22.6% of these women were as active as before treatment, 35.5% stopped any sexual activity and 41.9% experienced quantitative and qualitative changes. Analyses showed that each pattern had specific characteristics regarding current sexual functioning, the kinds of changes reported (e.g. decreased frequency and increased tenderness) and the reasons for these changes (e.g. tiredness and sex not a priority). Even in the immediate post-surgical period, women may react in very different ways to treatment in terms of sexual functioning. Most women experience changes, but cessation of sexual activity is not inevitable. Positive changes (growing tenderness and affection) also exist. These important interindividual differences require a person-centred approach when the topic of sexuality is being addressed, and practitioners need to be sensitive to individual perceptions of change. Early detection of sexual changes may prevent the crystallisation of difficulties over time.