Fear of an increasing disease progression (fear of progression) is among the main psychological stresses in patients with cancer, diabetes mellitus (type 1 and type 2) and chronic arthritis. The questions the study seeks to answer are: (1) Which are the main fears of these patients?, (2) How and in which circumstances in life do they occur?, (3) Which are the triggers of the fear? To answer these questions, a sample of 65 patients were researched through interviews. The results indicate that the predominant fears of cancer patients are the fear of dying and the unpredictability of the progression of the disease. Patients with chronic arthritis most frequently fear being physically dependent on someone else. The most common anxiety of diabetes patients are long-term complications. For all three groups of patients job-related fears cause a high amount of distress. These results contribute to the development of a standardised fear of progression questionnaire.