Background To investigate how cancer patients, family caregiver, and their treating oncologist view the risks and benefits of family involvement in cancer treatment decision making (TDM) or the degree to which these perceptions may differ. Patients and Methods A nationwide, multicenter survey was conducted with 134 oncologists and 725 of their patients and accompanying caregivers. Participant answered to modified Control Preferences Scale and investigator-developed questionnaire regarding family involvement in cancer TDM.