The purpose of a PMO is to provide a range of reporting and support services to one or more projects, programmes or portfolios.  Its main activities may range from simply providing project management support functions to being responsible for the direct management of project and programme managers.

In a number of major organisations a corporate PMO is established which often reports directly to the executive board.  This type of PMO not only performs a similar function to  ‘solo’ PMOs, providing information, but  may also provide advice and guidance, set and maintain standards for project management within the organisation, and provide ‘leadership’ to the project profession across the organisation.

At a divisional or functional level, PMO teams act as consultants to the projects and programmes being undertaken by the organisation.  They carry out reviews and health checks on projects to help ensure their success and the capture of lessons learned.
At a tactical level, solo PMOs provide support to individual projects or programmes, often in the form of administrative or specialist staff (e.g. planners, risk managers).