Introduction - Few studies have been conducted to date on the prevalence of use of complementary and alternative treatment methods (CAMs) in paediatric oncology, and those that have been conducted are often not representative. We therefore decided to study a representative sample of children with cancer in the German population.Patients and methods - The study took the form of a retrospective survey amongst all parents whose children were first diagnosed with a disease covered by the German Childhood Cancer Registry in 2001. The primary objectives of the survey were to establish the prevalence of use of CAM and the factors related to its use.Results - Of the 1595 questionnaires sent out, 1063 (67%) could be evaluated. 35% of the responders had used CAM. The most frequently used methods were homeopathy, dietary supplements and anthroposophic medicine including mistletoe therapy. Factors which increased the probability of using CAM were the previous use of CAM, higher social status and poor prognosis of the child’s disease. The most frequently named reasons for use of CAM were physical stabilisation, strengthening the immune system and improving the chance of cure. Whilst the sources of information about CAM were in most cases not doctors, 71% of users had nevertheless spoken to a doctor about using CAM. The effects of the CAM perceived by the parents were for the most part positive. 89% of the users reported that they would recommend CAM to other parents.Conclusions - CAMs are administered alongside standard therapy to 35% of children with cancer in Germany, usually by the parents. Prospective studies on the effects and side-effects of the most frequently used methods are urgently needed, and paediatric oncologists should have sufficient knowledge of CAM to enable them to advise parents professionally and competently about these treatments, too.