Radiotherapy can affect the electronic components of a cardiac implantable electronic device (CIED) resulting in malfunction and/or damage. We sought to assess the incidence, predictors and clinical impact of CIED dysfunction (CIED-D) following radiotherapy for cancer treatment. Clinical characteristics, cancer and different types of CIEDs as well as radiation-dose were evaluated. The investigation identified 230 patients; mean age 78±8 years and 70% were male.