The Project Management Office (PMO) is a relatively recent phenomenon, but over the last 10 to 15 years it has become a prominent feature in many organisations. Despite its proliferation, no consensus exists on how the PMO is best structured, what functions it should perform and, of particular importance, what value does the PMO contribute to the organisation. This research has been carried out to advance the existing body of knowledge in this field, specifically in relation to what functions the PMO performs in delivering value to the organisation. Using knowledge gleaned from the existing body of research in this field, the author has created the PMO Value Framework, a theoretical framework used to describe the functions or roles performed by PMOs. These roles are referred to as the PMO Value Roles. The author¿s hypothesis is that it is through performing these roles that the PMO delivers value to the organisation and as the PMO¿s ability to perform these roles improves the value delivered will increase. Using multiple case studies to test the theory the research found that PMOs perform the PMO Value Roles to different degrees and it is through performing these that the PMO delivers value to the organisation. Further, through improving the effectiveness of each role the PMO contributes to improving the project management competency within the organisation and thus helps develop organisational project management maturity. The PMO needs to develop a more significant strategic role within the organisation and is well placed to do so.