The literature on project success factors has largely ignored the impact of the project manager, and his or her leadership style and competence, on project success. This may be because most of the studies asked project managers their opinion and the respondents have not given due considera- tion to their own impact on project success. Or, it may be because the studies have not measured the impact of the project manager and, thus, not recorded it. Or, it may be because the project manager has no impact. However, that last conclusion is in direct contrast to the general manage- ment literature, which postulates that the leadership style and competence of the manager has a direct and measura- ble impact on the performance of the organization or busi- ness. Thus, the authors have been commissioned by the Project Management Institute to study whether the leader- ship style and competence of the project manager is a suc- cess factor on projects and whether different styles are appropriate on different types of projects.