This paper presents a new method to enrich semantically WordNet with categories from general domain classification systems. The method is performed in two consecutive steps. First, a lexical knowledge word sense disambiguation process. Second, a set of rules to select the main concepts as representatives for each category. The method has been applied to label automatically WordNet synsets with Subject Codes from a standard news agencies classification system. Experimental results show than the proposed method achieves more than 95% accuracy selecting the main concepts for each category.