s – It is important to know the contribution of a protected area to global conservation. A new method called ‘Relative Floristic Resemblance’ that uses databased and georeferenced herbarium specimens, is introduced. Its usefulness and applicability to assess the conservation value of protected areas is addressed. Method – This is tested using the collection database of the National Herbarium of The Netherlands (NHN) and species checklists of Gabon and of five national parks in Gabon and the Central African Republic. Results – The method proved to be a valuable instrument for revealing this conservation value, and can even, though with caution, be used for areas where a species list is still incomplete. We conclude that the four Gabonese parks are well chosen and each clearly conserve a different and comparatively unique flora. The Dzanga-Sangha Reserve captures a flora that ranges across a considerable part of the Congo Basin.Key words – Conservation, protected areas, Relative Floristic Resemblance, biodiversity, flora, collection database, Gabon, Central African Republic, Dzanga-Sangha.