Background In 2006, Croatia implemented AR-DRGs with the aim of increasing hospital output transparency, incentivizing efficient resource use, and measuring hospital performance and quality. Despite the intentions of this initiative, up until very recently, the hospital payment system continued to be based on historical budgets, although hospitals have been reporting inpatient activity using the DRG classifications. Only now is transition to a DRGbased payment system being planned. In 2013-2014, a Hospital Master Planning Project was undertaken to rationalize the hospital service delivery network and to improve efficiency. The Project also sought to create incentives to encourage the greater use of same-day inpatient services and improve the organization of the delivery of rehabilitation and palliative care services. The Project reported that the Croatian Health Insurance Fund (HZZO) does not have a strategy to encourage the utilization of same-day admissions. These services are primarily counted as part of the total DRG output for all admitted cases. Croatia uses AR-DRG version 5.2, which provides for 20 designated same-day DRGs. In the case of same-day surgical cases, the HZZO pays hospitals through two parallel systems. The first is through DRGs, where there are only 2 are same-day surgical groups (C15B and C16B); the second is through the outpatient system, which has 17 same-day surgical case categories that, in terms of clinical activity, are replicated in the DRG system. The use of both systems and their uncoordinated pricing creates a situation in which hospitals do not have financial incentives to increase the use of same-day surgical procedures. Recognizing that the increased use of same-day admissions would improve hospital efficiency, the Master Planning Project recommended that these admissions should be increased by 20% to 40% over a 3-year period. It appears, however, that these recommendations were made in the absence of a detailed analysis of the types of same-day procedures currently provided by hospitals. The Project did not recommend how hospital could increase their volume of same-day inpatient services, describe individual hospitals’ capacity to do so, or analyze hospital waiting lists.