Background As part of the EuroDRG project, researchers from 11 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 appendectomy 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 diagnosis of appendicitis treated with a procedure of appendectomy. DRG classification algorithms and indicators of resource consumption were compared for those DRGs that together comprised at least 97% of cases. Six standardized case vignettes were defined, and quasi prices according to national DRG-based hospital payment systems were ascertained. Results European DRG systems vary widely: they classify appendectomy patients according to different sets of variables (between two and six classification variables) into diverging numbers of DRGs (between two and 11 DRGs). The most complex DRG is valued 5.1 times more resource intensive than an index case in France but only 1.1 times more resource intensive than an index case in Finland. Comparisons of quasi prices for the case vignettes show that hypothetical payments for the most complex case vignette amount to only 1,005(sic) in Poland but to 12,304(sic) in France. Conclusions Large variations in the classification of appendectomy patients raise concerns whether all systems rely on the most appropriate classification variables. Surgeons and national DRG authorities should consider how other countries' DRG systems classify appendectomy patients in order to optimize their DRG system and to ensure fair and appropriate reimbursement.