In the 18th century Roman law suffered in Spain from two factors: first its rejection by the Absolute Monarchy and second: the influence of the Enlightenment on contemporary thinking. Whereas the Absolute Monarchists rejected Roman law because it did not stem from the sovereign himself, the followers of the Enlightenment considered the archaic laws neither compatible with current rationalist thinking: ‘Jusnaturalistic’ – nor practical for use in court. The predisposition against Roman legal tradition and in general the ‘ius commune’ provoked successive reforms to the law syllabus and diluted its influence greatly. We would thus imagine that the Spanish codification movement of the 19th century would have involved a radical break with Roman law – but this was not to be the case: conversely the legislators benefited from, and exploited it to the utmost, the result being that the most significant activities of codification were to become the overhauling and updating of justinian sources, ultimately leading to the founding of the Spanish legal system alongside those of many other European countries – on this very same, original Justinian Roman Law. This work, after analysing the peculiarities and vicissitudes of Spanish codification – clarifies didactically the great influence of Roman law in the Spanish Civil Code, the influence of which can be perceived both in its formal structure and content. The formal structure and lay-out of the Civil Code were inspired by the Institutes of Gaius- its contents are especially indebted to original Roman law in areas of: guardianship, curatorship; property classification, possession, methods of ownership acquisition, servitudes, usufruct and other personal servitudes, hypothec, concepts of inheritance and will testaments, legacies and forms of legacy, intestacy; concept and source of obligation, fault liability, theory of contract, contract types, quasi-contracts and extra-contractual liability.