OBJECTIVES: To assess and compare direct in-hospital costs in patients hospitalized with acute coronary syndromes (ACS; unstable angina or myocardial infarction), acute heart failure (AHF) and acute coronary syndromes complicated by heart failure (ACS with AHF) from health care payer perspective. METHODS: Patients hospitalized from 2005 to 2008 were classified in registry of Faculty Hospital Brno according to the clinical characteristics. Direct in-hospital costs (flat rate of admission and stay; medication and procedures) were evaluated in total 965 ACS (73% male; 64.7 years; 54% STEMI), 962 AHF (56% male; 70.8 years) and 808 AHF with ACS (62% male; 71.2 years; 61% STEMI) patients. The severity of disease was qualified as need of intensive care (ICU days); the predictors of high cost were identified in all groups. (1€=26CZK) RESULTS: Mean in-hospital cost was 101658CZK/3910€ in ACS pts (length-of-stay 5.6 days; 81% pts 2.3 ICU days; 0.3% died), 70201CZK/2700€ in AHF pts (length-of-stay 9 days; 48 % pts 4 ICU days; 11.4 % died) and 122340CZK/4705€ in ACS with AHF (length-of-stay 7.2 days; 92% pts 3.5 ICU days; 19.2% died). Percutaneous coronary intervention with stenting (PCI) formed more than 80% of total cost in ACS patients (performed in 78% pts.; 91% STEMI; 62% non-STEMI) and almost 60% costs in ACS with AHF pts (performed in 66% pts; 84% STEMI; 39% non-STEMI); antiarrhythmic interventions (incl. ICD, CRT BiV or PM device) made almost 50% cost in AHF although carried out in 8.6% pts. CONCLUSIONS: According to in-hospital costs patients with acute coronary syndromes complicated by heart failure were the most costly with maximum need of intensive care. Since 26.7% pts were transferred to other health care institution (e.g. 9% cardiosurgery) we expect the most significant increase of total amount of direct in-hospital costs in comparison with ACS (16.9% pts transferred) or AHF (11.5% pts transferred).