Developments in radiation oncology in recent years have highlighted the increasing deployment of personnel resources for tasks not directly related to patients. These tasks include patient-related activities such as treatment planning, reviewing files, and administrative duties (e.g., invoicing for services, documentation). The aim of the present study, part of the QUIRO project of the German Society of Radiation Oncology (DEGRO), was to describe, on the basis of valid data, the deployment of personnel resources in radiation oncology centers for "overhead" tasks. Questionnaires were used to analyze the percentages of time needed for various tasks. The target group comprised physicians, medical physics experts (MPE), and medical technical radiology assistants (MTRA). A total of 760 personnel from 65 radio-oncology centers in the German inpatient and outpatient sector participated (32 % physicians, 23 % MPE, and 45 % MTRA). High percentages of overhead tasks during working time were measured for each of the three personnel groups considered (physicians, MPE, and MTRA). Patient-related efficiency, i.e., the percentage of working time associated directly or indirectly with the patient, was highest among MTRA and lowest among MPE. Particular features could be seen in the activity profiles of personnel in university clinics. Duties in the areas of research and teaching resulted in a greater percentage of overhead tasks for physicians and MPE. Irrespective of function (physician, MPE, or MTRA), a managerial role resulted in lower patient-related efficiency, as well as a narrower time budget for direct patient care compared with non-managerial employees. Using the data gathered, it was possible to systematically investigate the time required for overhead tasks in radio-oncological centers. Overall, relatively high time requirements for a variety of overhead tasks were measured. These time requirements, generated for example by administrative duties or research and teaching, are currently not taken into adequate consideration in terms of remuneration or personnel capacity planning.