This research examines the relationship between the levels of IT maturity and the use of IS/IT investment evaluation and benefits realization methodologies via case studies and survey in the service sector. The findings indicate that IT maturity has a positive impact on the adoption of IS/IT investment evaluation and benefits realization approaches. A major contribution of this research is the development of an IS/IT maturity, investment evaluation and benefit realization methodologies matrix via the case studies. The matrix can assist service organizations in making and substantiating better business decisions. The relationship between the level of IT maturity and the use of IS/IT investment evaluation and benefit realization methods has been further tested and validated in the subsequent survey.