Ontologies are knowledge bodies describing the semantics of data and are broadly applied in supporting knowledge exchange between different parties. However, the adoption of the same ontology over a certain domain of interest by different people or organizations is unlikely, mainly due to the decentralized nature of ontology development. The paper presents a procedure for mapping hierarchical ontologies, populated with instances taken from properly classified text documents. It combines a structural and instance-based approaches in order to yield concept-to-concept mapping assertions between two input ontologies. It can be successfully applied to finding correspondences between the elements of two directories.