Mobile operators have been challenged since voice communication reached its peak and value added services became crucial for success. SMS is the most adopted value added service and responds for 80% of mobile data revenues in Brazil and in the world. This essay tries to understand customer`s motivation for adopting SMS service. An extended version of TAM - Technology Acceptance Model that includes the Perceived Quality Service and the Perceived Cost variables was analyzed in order to understand these factors. The software SPSS 13.0 helped to perform a multivariate data analysis and the structured equations were supported by the software AMOS 4.0. The analysis of results provides the following conclusions: Perceived Ease of Use, Perceived Service Quality and Perceived Cost influence the Attitude toward Using; Perceived Usefulness is the most relevant construct to determine the Attitude toward Using and the Behavioral Intention to Use; Behavioral Intention to Use is key driver to the construct Actual Use.