OBJECTIVES The aim of this study was to assess whether social media and disease-specific patient forums can be valuable sources of information on what matters to patients and caregivers about their disease and its management.  METHODS We investigated the accessibility of such information in breast cancer and schizophrenia. General social media websites and forums dedicated to sufferers of the two diseases were examined. RESULTS Breast cancer was more frequently mentioned in general social media websites than schizophrenia, with more charities, large organisations and fundraising events dedicated to breast cancer. Searches for breast cancer and schizophrenia on general social media sites result in hundreds of results, but these are mainly posted by advertisers or pharmaceutical companies, or contain non-patient opinions or news articles. Patients tend not to discuss their condition openly on general social media sites, whereas disease-specific forums contain daily entries on the patient experience. While searches within forums lead to fewer results, these are much more accessible and informative, and require less filtering through irrelevant posts. For example, posts from breast cancer patients typically discuss side effects of investigations and treatments and how to manage them, as well as offering emotional support. The limitations of using this type of information include the lack of a mechanism to confirm that contributors really do have the relevant disease, although the number of “factitious” patients is likely to be small and outweighed by “true” patients and caregivers. CONCLUSIONS This study showed that more valuable information can be found in patient-to-patient correspondence in forum threads than in general social media. Breast cancer patients appear to be more vocal in patient forums than schizophrenia patients, possibly due to the stigma attached to mental health problems. Little was found on what matters to breast cancer caregivers, since patients tend to present their own personal experience.