Affective computing is advancing as a field that allows a new form of human computer interaction, in addition to the use of natural language. There is a wide perception that the future of human-computer interaction is in themes such as entertainment, emotions, aesthetic pleasure, motivation, attention, engagement, etc. Studying the relation between natural language and affective information and dealing with its computational treatment is becoming crucial. In this paper we present a linguistic resource for a lexical representation of affective knowledge. This resource (named WORDNET-AFFECT) was developed starting from WORDNET, through the selection and labeling of the synsets representing affective concepts