The objectives of this study were to assess the additional use of alternative (complementary) therapies in patients with breast cancer who were receiving conventional treatment and to compare patients using alternative therapies with patients receiving only conventional treatment with special reference to psychological adaptation, causal attribution and quality of life. A sample of 117 female out-patients with a diagnosis of breast cancer filled in the following assessment instruments: FQCI (Freiburg Questionnaire for Coping with Illness), PUK (Causal Attribution Questionnaire), EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire), POMS (Profile of Mood States), and a self-developed questionnaire on alternative therapies. Nearly half the patients (47%, n = 55) reported that they had used alternative therapies in addition to conventional treatment. The methods applied most frequently were nutrition-related measures (special drinks, vitamin preparations and whole-foods - each applied by about 50% of users), mistletoe preparations (49%), trace elements (47%), and homeopathy (31%). Compared with patients receiving only conventional treatment, the users of alternative therapy were younger and better educated. Users developed a more active style of illness coping than nonusers and showed more religious involvement. Patients using a large number of alternative therapies (>3) tended to adopt a more depressive coping style than those using only a small number (< or =3). For a substantial proportion of cancer patients alternative therapies apparently fulfil an important psychological need. However, a subgroup of patients using many alternative therapies seem to have considerable adjustment problems. In dealing with cancer patients the treatment team should be aware of both these groups.