We aimed to determine the rate of Internet use for obtaining medical information by health-care patients at a tertiary paediatric hospital, whether the Internet may influence patients' attitudes to health-care services and health-care providers and whether patients would prefer the assistance of a professional informatics officer. An anonymous questionnaire randomly distributed to 450 subjects at Sydney Children's Hospital, Sydney, Australia. A total of 294 (65%) questionnaires were returned. Overall Internet use for medical information was 64% (189/294). Most (97%; 183/189) respondents reported 'wanting to know more' as the reason they sought information on the Internet. Eighty-eight per cent (167/189) of respondents reported that they trust their doctor more than the Internet. Twenty-one per cent (39/189) had presented their doctor with information about which he/she was unaware and 18% (34/189) had altered a health-care decision because of information found on the Internet. The Internet had influenced questions asked of doctors in 83% (156/189). Eighty-six per cent (252/294) of all respondents were in favour of professional assistance to obtain medical information. A large number of patients use the Internet to find information that influences their attitudes to health care. The services of a medical informatics professional would likely benefit both patients and doctors.