The purpose of this paper is to present some ideas and hypothesis about two theoretical models describing how advertising works : the "learning model" (according to which advertising works on consumer attitudes, which in turn works on consumer behaviour) and the "minimal involvement model" (according to which advertising works directly on consumer purchase without going through a change of attitudes). Individuals may differ widely in their areas of interest, and individual's interest in a given subject dictates to a great extent his attitudes and reactions to products, advertisements and promotions which cover this area of interest. The level of consumer involvement for a given product results from his own combination of interests. This differentiation according to involvement level leads to the description of two representative types of consumers (highly involved and lowly involved) in terms of attitudes towards the product, towards advertising or informations concerning the product, and purchase behaviour. Marketing communication works differently on these two types of consumers. Among the consumers of the same product, the highly involved tend to react according to the learning model, and the lowly involved according to the minimal involvement model. Media and advertising messages have different communication abilities according to the involvement level of the consumers reached, and promotional campaigns have different effects. The significant differences between highly involved and lowly involved consumers make it necessary for communication strategies to take into account the concept of involvement.