Social annotations voluntarily provided by users in tagging or book-marking sites such as Delicious or Flickr have been recognized as an interesting source of metadata for assisting tasks such as classification of Web resources. However, the open-ended nature of the tags employed to annotate resources leads to problems such as the introduction of noise and ambiguity that may hinder clas- sification results. This paper presents an approach for semantically analyse social annotations in order to attain enriched, concept-based representations of Web resources. Experimental results showed that the strategies proposed to relate tags to conceptual entities allow to improve the results of resource classification.Sociedad Argentina de Informática e Investigación Operativa