Korea has been ranked at the top consecutively in UN e-Government Survey. This fact reflects consistent efforts by public institutes in Korea. However, there were some duplicate efforts and inefficiency in the investment into IS(information systems). In other words, management and decision making on e-government have yet to improved. Accordingly, governmental institutes have long been promoting policies for EA in order to carry out and manage effectively IT projects including the e-Government projects. EA is being regarded as a means to facilitate IT Governance for systematic management of IT projects, A major objective is to firmly establish the decision making process for IS investment through EA, since the each institute is a large organization with so complicated and specialized demand for IS. As a result, systematic decision making is becoming quite difficult. Thus, this study attempts to identify different types of IT investment decision making and to figure out the relationship between the decision types and the organizational performance of public institutes where EA was implemented.