Cancer and its management affect patients’ cognitive resources and education needs in several ways. The objective of this study is to identify significant factors affecting cognitive resources and knowledge expectations of adult patients with cancer during the course of their illness trajectory. Current or former patients with cancer (n = 53) were recruited to focus group interviews and individual in-depth interviews. The informants’ knowledge expectations vary during their illness trajectory and are affected by personal, situational, and clinical factors. These should be acknowledged to provide person-centered, holistic nursing care and patient education.