The study evaluated the illness behavior of patients with celiac disease and the influence of the disease and its treatment on key personality components and adherence to dietary recommendations. Twenty-nine adult patients with celiac disease and 47 matched healthy comparison subjects participated in the study. More than 70% of the celiac disease group scored in the pathological range on at least one scale of the Illness Behavior Questionnaire. Patients who received the diagnosis in adulthood had a lower score for nonconformism, a greater tendency to pretend to be sociable, and higher levels of psychophysiological reactiveness, relative to the comparison subjects. The results suggest that celiac disease may be associated with changes in personality that may interfere with patients' adaptation to living with a chronic disease.