This work was made from a bibliographic analysis and statistical reports to determine whether advertising in search engines or by its acronym in English Search Engine Marketing (SEM), affect the decision to purchase consumers in Colombia and the world. Likewise, the price sensitivity or price elasticity of the demand is analyzed in the consumer's purchase decision for purchases made through web sites arranged for electronic commerce Ecommerce; or at physical points of sale, starting from the search engines to make a more informed purchase decision. It also explains the scope of advertising in search engines, increases in budgets that guide organizations for this area and the growth that has had advertising in marketing companies to establish the internet as a dynamic and open sales channel to reach the consumer through succinct and direct messages. Finally, the reader will be able to observe a report distributed in four (4) chapters: the first chapter explains the antecedents and main attributions of the increase of advertising in search engines; in the second chapter, the way in which advertising in search engines affects the decision of purchase of users or consumers is explained; in the third chapter, a profile of the price elasticity of the demand is made, exposing the term and its condition in front of the advertising in search engines and the decisions of purchase of the consumers; Finally, the fourth chapter describes the return to investment made by organizations to use SEM advertising.