Web advertising, one of the major sources of income for a large number of Web sites, is aimed at suggesting products and services to the ever growing population of Internet users. A significant part of Web advertising consists of textual ads, the ubiquitous short text messages usually marked as sponsored links. There are two primary channels for distributing ads: Sponsored Search (or Paid Search Advertising) and Content Match (or Contextual Advertising). In this paper, we concentrate on the latter, which is devoted to display commercial ads within the content of third-party Web pages. In the literature, several approaches estimated the ad relevance based on co-occurrence of the same words or phrases within the ad and within the page. However, targeting mechanisms based solely on phrases found within the text of the page can lead to problems. In order to solve these problems, matching mechanisms that combine a semantic phase with the traditional syntactic phase have been proposed. We are mainly interested in studying the impact of the syntactic phase on contextual advertising. In particular, we perform a comparative study on text summarization in contextual advertising. Results show that implementing effective text summarization techniques may help to improve the corresponding contextual advertising system.