OBJECTIVES To evaluate the degree to which the officially pre-determined cost and average length of stay (ALoS) per selected KEN-DRG reflect actual resource use and to investigate other factors (e.g. size, type and location of hospital) correlated with charges and ALoS. METHODS Data were from the Health Regions data base and included discharges, ALoS, and charges in NHS Hospitals for the selected KEN-DRGs. Predetermined ALoS and cost per KEN-DRG were derived from Gazette 946/27/03/2012. Continuous variables did not follow normal distribution, so non parametric methods (Spearman's correlation coefficient, Kruskal-Wallis test and Mann-Whitney test) were used. A two sided p-value ≤ 0.05 was considered statistically significant. RESULTS Higher length of stay compared with the officially pre-determined was found for Chronic Obstructive Pulmonary Disease (COPD) with complications (10.8 vs 9 days), Bronchitis & Asthma with complications (5.8 vs 4 days), Bronchitis & Asthma without complications (2.7 vs 2 days) and Breast Cancer with complications (7.9 vs 5 days). Consequently, officially pre-determined cost for Breast Cancer with complications (€965), Bronchitis & Asthma with complications (€792)  and COPD with complications (€1,446) represents less than 90% of total hospital charges (total actual average charge: €1,186; €929; €1,634 respectively). However, for the rest of the DRGs, under study, there were none or limited additional hospital charges. For all KEN-DRGs, size and population density was positively correlated with total charges (r_s=0.12, p=0.018 ; median for Athens =863 & semi-urban=752 p=0.09 respectively). Moreover, for Bronchitis & Asthma with and without complications, population density was found to be positively correlated with ALoS (median for urban areas=5.1 and semi-urban=4.7; p=0.09 and median for urban areas=3 and semi-urban=2.5; p=0.03 respectively). CONCLUSIONS The introduction of KEN-DRGs was a useful first step to modernize the hospital reimbursement system. However, further revisions are required in order for KEN-DRGs to become more useful.