Hyperthermia, increasing tumor temperatures to 40-43°C, is a proven oncological treatment modality enhancing the effectiveness of radiotherapy and chemotherapy. Tumors are usually heated by single radiofrequency or microwave antennas, or arrays of antennas around the patient. Reliable hyperthermia treatment planning by simulation of power and temperature distributions in the patient, requires the availability of patient-specific input data. This paper focuses on the progress made in acquiring accurate patient models for the electrical properties and their impact on hyperthermia treatment planning.