This is a video blog but focusing on a concept outlined in the PMBOK Guide that categorizes PMOs as Supporting, Controlling, or Directing.
General categorization could be useful, however, it can be misleading. For example, we have recently received a request for proposal where a company established a PMO less than three years ago and now they want to change it from Supporting to Controlling. This is fine, in theory, but in practice – what does that mean?
Our preference is that organizations must focus on purpose, mission, vision, of what they want the PMO to accomplish for them. Maybe they do not need a PMO but a PM Department or Division. On the other hand, maybe a secretary or analyst can do the work for them – or outsource it.
What we are saying is that a PMO must be adaptive, like project management, and must be unique to organizational context.