From January 2015 to January 2017, we encountered five terminal cancer patients with implantable cardioverter defibrillators (ICDs) in the palliative care unit of our hospital. Due to delirium or dementia, four of these five patients did not have the decision-making capacity to stop their ICD. Although one patient was capable of making his own decisions, his family did not agree with the medical professional considering the patient’s decision. The families of all five patients made decisions on behalf of the patients. The procedure for stopping the ICD was first discussed with the families at 2–21 days prior to the patients’ deaths. The ICDs were stopped between 3 h and 11 days prior to the patients’ deaths, following the consent of the families, which was obtained after 1–5 consultations. Through these experiences, we became aware of the following problems with regard to stopping ICDs: (1) the lack of experience of medical professionals in decision-making, (2) the lack of recognition of medical professionals to the distress caused to patients by ICDs, (3) the psychological burden and time constraint of discussions, and (4) the lack of knowledge of ICDs among patients and their families. These problems need to be addresses as part of advance care planning for cancer patients.