Background: It is a well-known phenomenon that nurses and other oncology staff have a tendency to ascribe patients with cancer more problems and suffering than the patients themselves report. Aim: The overall aim of the present thesis was therefore to gain increased knowledge and understanding of dis/agreement between patients with cancer and nurses regarding their perception of patients’ situation and of the importance of patient-nurse dis/agreement in clinical practice. Methods: A prospective comparative design was used. Data were collected from a sample of 90 consecutively recruited patient-nurse pairs. Each pair consisted of a patient with cancer, newly admitted to a ward, and a nurse responsible for that patient’s care. Data were collected from the pairs with corresponding self-administrated questionnaires on two occasions: directly after the admission interview and on the patient’s third day on the ward. Results: At the group level, a distinct pattern was shown in which nurses ascribed the patients more emotional distress, less coping resources and a lower quality of life than the patients themselves reported. In short, the results revealed the following clinical importance of patient-nurse dis/agreement. With respect to how nurses act in relation to their perceptions of patients’ emotional distress, patient-nurse dis/agreement did not seem to be important; with few exceptions, nurses’ implemented care did not differ when it was directed at more as compared to less distressed patients. Further, nurses’ general tendency to overestimate cancer patients’ problems and suffering had no influence on patients’ satisfaction with received care and nurses’ satisfaction with provided care. However, patients cared for by nurses who underestimated their level of depression were less satisfied with those nurses’ care. In addition, the more frequently the nurse had implemented care characterized by a trusting relationship, the higher patients’ and nurses’ satisfaction with received/provided care. Conclusions: Initial patient-nurse dis/agreement concerning patients’ situation appears to be of little significance to nurses’ caring behaviour and to patients’ and nurses’ subsequent evaluation of received and provided care.