Based on two qualitative studies, this article describes the significance of fellow patients in cancer wards, and the relevance for health personnel involved in patient-patient relationships is discussed. Using grounded theory, in-depth interviews were conducted in the first study with 21 adult cancer patients and in a follow-up study with 8 patients and 27 health care providers. The findings indicate that the significance of fellow patients for the patient with cancer can be described in terms of three different dimensions: attitudes toward own illness, interpersonal relationships, and environmental factors. Although contact with fellow patients most often seems to engender positive experiences, some negative experiences are reported also. The suggestions in this article for practical implications are meant to help nurses and other health care providers to promote positive and prevent negative consequences in patient-patient relationships in hospitals.