It is not clear whether psychiatric comorbidity in medically ill patients contributes to longer lengths of hospital stay (LOS), and whether interventions carried out by psychiatric consultation-liaison (c-l) services lead to a reduction of LOS. Furthermore, the lagtime paradigm, i.e. the notion that the earlier a psychiatric consultation takes place, the shorter LOS of the resp. patients are, has been questioned. To study if different degrees of somatopsychic comorbidity have effects upon Lagtime and LOS of patients seen by a c-l-psychiatric service. Patients consecutively referred to a c-l-service in Berlin during a one year study period were categorized into six groups of different somatopsychic comorbidity using a count-approach based upon ICD-10 psychiatric, and ICD-9 somatic diagnoses. The groups with more psychiatric than somatic diagnoses show shorter LOS and shorter Lagtimes. Patients with only psychiatric diagnoses overall show the shortest average LOS and Lagtime. For the groups, however, with more somatic than psychiatric diagnoses, LOS and lagtimes are longer. In the groups with equal numbers of psychiatric and somatic diagnoses, there is a trend with higher numbers of somatic diagnoses showing longer LOS and Lagtimes. On the other hand, in both groups with 2 and more somatic diagnoses, a trend can be seen toward shorter LOS and Lagtimes in such patients with more than 1 psychiatric diagnosis. Psychiatric comorbidity in medically ill patients does not sufficiently explain differences in LOS and Lagtime of patients seen in psychiatric c-l-services, but a complex interplay of somatopsychic comorbidity has to be taken into account.