Aim: To evaluate temporomandibular disorder (TMD) patients for differences between masticatory muscle (MM) and temporomandibular joint (TMJ) pain patients in the prevalence of post-traumatic stress disorder (PTSD) symptoms and evaluate the level of psychological dysfunction and its relationship to PTSD symptoms in these patients. Methods: This study included 445 patients. Psychological questionnaires included the Symptom Check List-90-Revised (SCL-90-R), the Multidimensional Pain Inventory, the Pittsburgh Sleep Quality Index, and the PTSD Check List Civilian. The total sample of patients was divided into 2 major groups: the MM group (n = 242) and the TMJ group (n = 203). Each group was divided into 3 subgroups based on the presence of a stressor and severity of PTSD symptoms. Results: Thirty-six patients (14.9%) in the MM group and 20 patients (9.9%) in the TMJ group presented with PTSD symptomatology (P = .112). Significant differences were found between the MM and the TMJ group in several psychometric domains, but when the presence of PTSD symptomatology was considered, significant differences were mostly maintained in the subgroups without PTSD. MM and TMJ pain patients in the "positive PTSD" subgroups scored higher on all SCL-90-R scales (P .001) than patients in the other 2 subgroups and reached levels of distress indicative of psychological dysfunction. TMJ pain patients (58.3%; P = .008) in the positive-PTSD subgroups were more often classified as dysfunctional. Both positive-PTSD subgrounps of the MM and TMJ groups presented with more sleep disturbance (P .005) than patients in the other 2 subgroups. Conclusion: A somewhat elevated prevalence rate for PTSD symptomatology was found in the MM group compared to the TMJ group. Significant levels of psychological dysfunction appeared to be linked to TMD patients with PTSD symptoms. Schlagwörter: prevalence, post-traumatic stress disorder, psychological dysfunction, sleep disturbances, temporomandibular disorders