When developing semantic applications, constructing the underlying ontologies is a crucial part. Construction of both Semantic Web and enterprise ontologies need to be semi-automatic in order to reduce the effort required and the need for expert ontology engineers. Another important issue is to introduce knowledge reuse in the ontology construction process. By basing our semi-automatic method on the principles of case-based reasoning (CBR) we envision a novel semi-automatic ontology construction approach and also a novel application of case-based reasoning. The development of OntoCase is still ongoing work, in this paper we report mainly on the motivation for using CBR and the possible benefits of this.