Objectives: The purpose of this study is to determine how cancer patients perceive their illness and factors affecting the perception illness. Methods: The study was a descriptive and cross-sectional study. Data were collected Erzurum Atatürk University Research Hospital Medical Oncology Clinic between February and September, 2010. The study population was consisted of 192 cancer patients, who was over 18 years of age, who understand and can speak Turkish, without any psychiatric illness diagnosis and awareness of th eillness. Data collection tools were Patient Quastionnaire and İlness Percepitions Questionnaire. Results: Since the beginning of the disease patients experienced fatigue symptoms and associated this symptom with their illness. When examined subscales related to their views on the disease patients; the score mean for perception of personal control and perception of consequences all sub-scales regarding the patients’ view on their illness, was higher in comparison to all other sub-scales of the scale. The score mean for perception of time (cyclical) and perception of illness coherence was the lowest. Risk factors attributions were determined as the most common reasons behind the patient illness. Conclusion; It is determined high internal control on duration of illness and course illness, treatment. It is determined low understanding of illness.