Background Medical psychiatry units (MPU) provide integrated care for hospital patients with medical and psychiatric comorbidity. Lack of an empirically validated MPU typology hampers comparison of their (cost-)effectiveness. Methods A recent database on the organization of Dutch MPUs was used to empirically validate the MPU typology of Kathol (Model 1), develop types on the basis of the medical and psychiatric capabilities underlying this typology (Model 2), and to develop types from the data using k-means clustering (Model 3). Results Dutch MPUs are most alike the type III/IV MPUs described by Kathol. However, these types appear hardly distinctive for the Dutch context. The more generic approach of Model 2 provides comparable results. Both models show that the majority of Dutch MPUs handle moderate to high level medical and psychiatric acuity and can be classified as Complexity Intervention Units (CIUs). Model 3 yields three clusters to best characterize the Dutch field: CIUs with coercive admission facilities and 24/7 availability of ECT, CIUs without these facilities but with grossly comparable medical capabilities, and a smaller group of low acuity MPUs. Conclusions Kathol distinguished two types of CIUs (types III and IV MPUs) on the basis of medical acuity capabilities. This study reveals that psychiatric capabilities are most distinctive for the two high acuity MPU-types encountered in The Netherlands. In addition, a modest number of low acuity MPUs was found. Repeating our analysis in other countries is called for, as well as using the newly identified types for (cost)-effectiveness analysis in the Dutch context.