Background: The objective of this study was to compare the effectiveness of psychodynamic and behavioral inpatient treatments of severely obese patients regarding weight and distress. Methods: In a longitudinal study obese patients (body mass index, BMI ≧35) were randomly assigned to behavioral or to psychodynamic inpatient treatment. Mostly female (n = 267; 85%) obese patients with psychiatric and somatic comorbidity (age 20–64 years, BMI 35–74) were examined with standardized self-report scales on distress (SCL-90R), interpersonal problems (Inventory of Interpersonal Problems), eating behavior (Fragebogen zum Essverhalten) and body image (Fragebogen zum Körperbild). Results: During 49 days (mean) of inpatient treatment, patients lost an average of 5.6 kg (4.4%) in the behavioral (n = 130) and 5.7 kg (4.4%) in the psychodynamic setting (n = 137). In both settings, eating behavior, well-being and body image also improved significantly. One year after discharge, return rate was 73%. Forty percent had further reduced their weight (by more than 5% compared to intake), 36% had regained weight, but were still below intake level, and another 24% had increased weight above intake. Conclusion: Behavioral and psychodynamic treatments were equally effective reducing weight and distress over 1 year.