ContextExisting measurements of patient preferences cover only a limited range of health information and participation in decision making. A broader approach is necessary to understand the breadth and variations in patient preferences.ObjectiveTo explore the breadth and variances in patient preferences for health information and participation in decision making and to understand the relationship between age and each type of preference.DesignThe Health Information Wants Questionnaire (HIWQ) was administered during May–December 2010 to gather data about the information and corresponding decision‐making autonomy participants would want in seven areas: diagnosis, treatment, laboratory tests, self‐care, complementary and alternative medicine (CAM), psychosocial factors and health‐care providers.SettingA large state university, public libraries and senior centres in Maryland, USA.ParticipantsA convenience sample of 438 individuals, including 226 undergraduates (mean age = 20; SD = 2.15) and 212 community‐dwelling older adults (mean age = 72; SD = 9.00).Main Outcome MeasuresRatings on the information and decision‐making items of the HIWQ.ResultsParticipants expressed higher levels of preference for information than for participation in decision making on six of seven subscales. On the psychosocial subscale, they expressed stronger desire for participation in decision making than for information. Age had no predictive effect on the overall preferences or specific preferences for information and participation in decision making about standard treatments and CAM. The predictive effect of age on the other types of preferences varied significantly.ConclusionsPhysicians should take into account the breadth and variations in patient preferences. The predictive effect of age on patient preferences varied depending on the specific area of preferences.