Objectives: The aim of this study is to compare patients with fibromyalgia, their first degree relatives; osteoarthritis patients, their first degree relatives; patients with somatization disorder and healthy controls in terms of psychological symptoms, somatic complaints and ways of coping with stress. Materials and Methods: The study is planned as crosssectional.Patients who presented to the Düzce University Faculty of Medicine, Physical Medicine and Rehabilitation Outpatient Clinic between June 2016 and January 2017 and who diagnosed with fibromyalgia and osteoarthritis, and their first-degree relatives, patients with somatization disorders and a healthy control group who filled out the informed consent form was included in this study. The socio-demographic information query form, Coping Inventory for Stressful Situations (COPE) Form, Psychological Symptom Checklist (SCL-90) and the Visual Analog Scale (VAS) were applied to all volunteers. Covariance analysis was used to compare groups in terms of scale scores. Results: It was determined that the groups were not homogeneous in terms of age, VAS, education level, sex, marital status and occupation. The groups were compared taking into account the impacts on the COPE and SCL-90 scores of these characteristics which are thought to be confounders. As a result of the evaluations, it was determined that the patients with fibromyalgia and somatization preferred the problem-focused coping and emotional-focused coping attitudes significantly less and the non-functional coping attitude significantly more. Osteoarthritis patients were found to be in the middle of both sides on many occasions. However, there was no significant difference among the groups in terms of psychological symptoms when the effect of the confounding factors were eliminated. Conclusion: Since the findings achieved suggest that fibromyalgia and somatization disorder are the same diseases, it has been concluded that more research should be conducted on the subject.