BACKGROUND As part of the EuroDRG project, researchers from eleven countries (i.e. Austria, England, Estonia, Finland, France, Germany, Ireland, Netherlands, Poland, Sweden, and Spain) compared how their Diagnosis-Related Groups (DRG) systems deal with cholecystectomy patients. The study aims to assist surgeons and national authorities to optimize their DRG systems. METHODS National or regional databases were used to identify hospital cases with a procedure of cholecystectomy. DRG classification algorithms and indicators of resource consumption were compared for those DRGs that individually contained at least 1% of cases. Six standardised case vignettes were defined, and quasi prices according to national DRG-based hospital payment systems were ascertained and compared to an index case. RESULTS European DRG systems vary widely: they classify cholecystectomy patients according to different sets of variables into diverging numbers of DRGs (between two DRGs in Austria and Poland to nine DRGs in England). The most complex DRG is valued at four times more resource intensive than the index case in Ireland but only 1.3 times more resource intensive than the index case in Austria. CONCLUSIONS Large variations in the classification of cholecystectomy patients raise concerns whether all systems rely on the most appropriate classification variables. Surgeons, hospital managers and national DRG authorities should consider how other countries' DRG systems classify cholecystectomy patients in order to optimize their DRG systems and to ensure fair and appropriate reimbursement.