A high rate of psychiatric comorbidity is found in patients with somatic diseases in general hospitals. Reasons for psychiatric disorders in somatically ill patients are variable and can lead to or be a result of the physical illness or just occur coincidentally. Consultation-liaison services (C/L) assist the physician and the treatment team on internal surgical wards in general hospitals in paying attention to and caring for somatic psychiatric comorbidities with diagnostic, therapeutic and, if appropriate, secondary preventative methods. In this article an overview of the development of C/L psychiatry is given. Furthermore, the importance of particular psychiatric disorders seen by psychiatric C/L services and their treatment is described. Finally, specific aspects of service delivery with regard to collaborative care between general hospital physicians and private practitioners are discussed.