A comparison of chronic pain patients in outpatient and inpatient treatment settings regarding pain-related and psychological characteristics, has not yet been systematically analyzed. The core documentation and quality assurance in pain therapy (KEDOQ-Schmerz) is a quality assurance system for documentation and quality management of pain therapy in different treatment settings. The system was initiated by the German Pain Society. We used KEDOQ-Schmerz data to describe differences between patients being treated in outpatient and inpatient settings with respect to social, pain-related and psychological factors. In total, the set of KEDOQ-Schmerz data analyzed included information from 4705 patients (from 13 clinics) collected between January 2012 and April 2016. Patients received either outpatient (n = 2682) or inpatient (n = 2023) treatment. The data analyzed comprised sociodemographic, pain-related and psychological data collected through the German Pain Questionnaire (DSF) at the beginning of treatment as well as information about pain chronification and pain localization provided by practitioners. The statistical analysis was carried out by descriptive and comparative data analysis using univariate and multivariate statistical methods. Patients with inpatient treatment were significantly older, more often female and more often had multiple pain localizations. They described stronger pain intensity and more frequently had a higher Mainz Pain Staging System (MPSS) score of pain chronification. They described a significantly poorer physical and mental health-related quality of life in the short form (SF-12) health survey, had significantly higher depression, anxiety and stress values (DASS) and a poorer habitual well-being in the Marburg questionnaire on habitual well-being (MFHW). Significant group differences had only small effect sizes. Even though most predictors for the inpatient treatment setting in multivariate analysis were significant, in total they explained less than 5% of the variance. The results indicate that pain therapy in specialized pain settings more and more has to manage patients with higher pain chronification, higher pain-related stress and previous therapy experience. The differences in patient characteristics between treatment settings are mostly clinically unimportant. Differences in clinical features do not declare the allocation to one treatment setting or the other.