The aim of this study was to determine the prevalence of complementary and alternative medicine (CAM) use among children with cancer who had received or were receiving treatment at a large hospital in the UK, including the identification of the most commonly used therapies and parental motives for doing so. Using a cross-sectional survey design, questionnaires were sent to parents of paediatric patients diagnosed with cancer. Of the 49 respondents, 32.7% reported using some type of CAM. The most commonly used therapies included multivitamins, aromatherapy massage, diets and music as therapy. Most children had used more than one therapy. Many of the factors that motivated parents to use CAM were related to helping or supporting their child's medical treatment. The main benefits identified from using CAM included increased confidence, pain relief and relaxation. The longer the time since diagnosis the more children tended to use CAM. The reasons for parents not using CAM included the child doing well and therefore not seeing the need for CAM use; not being aware of CAM; CAM not being offered and lack of information available. Parents identified a need for more information to be available both at ward level and for information about CAM to be discussed by medical staff, particularly at the start of treatment. The results indicate that CAM is frequently used by children and young people with cancer and that their use plays a substantial role in helping children through their conventional cancer treatment.