OBJECTIVES: To estimate the hospitalisation cost of ICU patients admitted to the TUHL in the region of Thessaly, in Greece. METHODS: The ICU chosen is the only tertiary university ICU in the whole region of Thessaly accounting 27% of the total ICU beds. The study sample consisted of all patients (elective and emergency admissions) admitted to the respective TUHL in 2006. Clinical data were derived from patients’ medical records on a retrospective basis whereas economic data were derived from the Hospital’s Financial Department. The analysis included direct costs, using an up-down approach under NHS perspective. The nominal and actual hospitalization cost per ICU patient were based on the resource utilisation and the annual hospital balance sheets on NHS prices in Euros. RESULTS: 312 have been admitted to the ICU with a total direct cost of €4,799million suffering from stroke, COPD, cancer, heart, trauma, pneumonia with a mean length of stay 8.87 days. The mean cost per hospitalisation day in the ICU was estimated at €1,734. Mean actual cost per patient is estimated at  €15,382 whereas social insurance funds reimburse only €1,666.  Personnel costs are the major cost component accounting for 31% of the total cost, while the pharmaceuticals account for 23%, laboratory 11%, supply and oxygen 17%, infrastructure-hotel services expenses 18%. CONCLUSIONS: This research results in some meaningful conclusions for effecting changes in hospital policies for better utilization of ICU resources, for optimizing patient care and incorporating economic assessment in decision-making.