Disturbed sleep and (morbid) obesity are increasing health problems in industrial societies and play an important role in chronic illnesses. Conclusive evidence about their relationship is lacking. The aim of this study was to investigate the relationship between insomnia and obesity and if common associated factors such as psychological distress, self-control, attachment insecurity, and socioeconomic status are present to the same extent in both patient groups. The sample consisted of 177 patients referred to the Medical Psychology department of a general hospital (92 with morbid obesity and 85 with insomnia). Measures used were PSQI, HADS, BSCS, PSWQ, DERS, and ECR-M16. Results showed that morbid obesity and insomnia are largely unrelated health risks, with little overlap in associated factors and divided mainly by SES. This indicates that condition-oriented interventions rather than transdiagnostic interventions are likely to be more effective and that different population groups (high vs low SES) may benefit from different approaches.