The diagnosis of cancer in many cases provokes a crisis, resulting in an increase of regression and defence mechanisms (splitting, projective identification, projection, denial, repression). This article reviews the increased sensitivity, the partial and temporary narrowing of consciousness, and the weakening of reality control. In many cases fluctuating depersonalisation and derealisation develop. At our Institute we performed a complex psychological examination of 41 patients, suffering from malignant lymphoma, immediately after informing them of the diagnosis but prior to their first treatment. The psychological examination of volunteering patients involved an initial interview, Rorschach and Szondi projective tests, a Wechsler intelligence test and a discussion of the results with the patient. The relatively frequent temporary pathological psychic conditions exert an influence on the decisions of patients make about their treatment and interventions, and may also influence the doctor patient relationship.