The purpose of this study was to describe what kind of information radiotherapy patients expected to receive through Internet education. Questionnaire data for the longitudinal study were collected from patients at the beginning (stage 1), in the middle (stage 2), and at the end (stage 3) of their radiotherapy period. In stage 1, a total of 150 questionnaires were handed out, and 100 were returned, giving a response rate of 67%. Of the 100 patients, 75 and 73 completed the questionnaires in stages 2 and 3, respectively. Descriptive statistics and content analysis were used in data analysis. Knowledge expectations could be classified into four: "I have no expectations," "I don't know what I want," "I want all possible available knowledge," and "I want specific knowledge from different issues." "I want specific knowledge from different issues" were biophysiological, functional, social, experiential, ethical, and financial areas. Patients' information expectations were highest in the biophysiological, functional, and social areas and lowest in the experiential, ethical, and financial areas. Expectations varied during radiotherapy. Characteristics' variables of patients associated with expectations. This study can contribute toward the development of an Internet site based on the knowledge expectations of radiotherapy patients. The results can also be used in individual patient education.