Introduction: The aim of the international CORE project was to explore the databases of the existing hernia registries and compare them in content and outcome variables. Methods: The CORE project was initiated with representatives from all established hernia registries (Danish Hernia Database, Swedish Hernia Registry, Herniamed, EuraHS, Club Hernie, EVEREG, AHSQC) in March 2015 in Berlin. The following categories were used to compare the registries: initiation and funding, data collection and use for certification of hernia centers, patient data and data protection, operative data, registration of complications and follow-up data. Results: The Danish Hernia Database is the only one to qualify as a genuine national registry where participation is compulsory for entry of all procedures by all surgeons performing a hernia operation. All other registries have to be considered as voluntary and completeness of data depends upon the participating hospitals and surgeons. Only the Danish Hernia Database and the Swedish Hernia Registry are publicly funded. All other registries are reliant on financial support from the medical technology industry. As an incentive for voluntary participation in a hernia registry, hospitals or surgeons are issued a certificate confirming that they are taking part in a quality assurance study for hernia surgery. Due to data protection and privacy regulations, most registries are obliged or have chosen to enter their patient data anonymously or coded. The Danish Hernia Database and Swedish Hernia Registry utilize a national personal patient code. In the Herniamed Registry, patient data are saved in a coded and anonymous format after obtaining the patient’s informed consent. Conclusion: Despite the differences in the way data are collected for each of the listed hernia registries, the data are indispensable in clinical research.