Figure 2: pmo types (Desouza&Evaristo, 2006)

Supporters’ functions usually include the basic administrative issues such as defining risks, monitoring the project performance, archiving and providing information. Although these offices are responsible for the project implementation, in fact, they play passive role and cannot influence the project management process that put to question their usefulness for the organization.

Moving to the Information manager it’s necessary to mention that although it is situated in between the administrative and knowledge roles and partly carry out both functions still it is concerned with collecting information and analyzing the project progress and lacks the managerial authority.

Knowledge manager is situated more closely to the knowledge-oriented edge and, subsequently, does not carry out administrative functions. Mainly, it serves as the best practices storage and on their basis may reorganize project portfolio or be responsible for the successful implementation of individual projects. The main difference between information manager and knowledge manager consists in the type of information collected. While the first is concerned with information on project performance the latter mainly accumulates and analyzes information on the project management methods and techniques.

Coach type is similar to the coach model mentioned above described by Kendall and Rollins. Serving as the knowledge depository this office is also responsible for implementation of best PM practices. Talking about this kind of offices it’s necessary to highlight that from change management perspective it usually acts as a change agent moving organization to new levels of project management maturity and overcoming resistance.

Finally, we would like to describe one more, quite recent, typology of PMOs based on several variables proposed by Hobbs and Aubry in their study of 500 project management offices around the world. According to the outcomes of the study the researchers have proposed to classify PMO types on the basis of organizational context variables, such as sector, size, type of organizational structure and level of PM maturity, and characteristics of PMO, including its size, number of projects managed, position in organizational structure and authority level. Hence, three main PMO types have been defined:

1. PMOs with a considerable number of projects, project managers and significant authority in decision-making process

2. PMOs with an average number of projects, not many project managers and less power in making decisions

3. PMOs with a small amount of project managers responsible for projects in organization with a low level of authority in decision-making process.

Drawing the parallels it is possible to mention that the first type of PMO mentioned is similar to strategic or enterprise project management office, while the last one could be compared with the administrative-oriented office. Talking about the classification provided it could be said that some issues could be controversial, however, according to the authors the classification given is not final and requires further research efforts.

To summarize it is possible to conclude that a large variety of criteria can be used for PMO classification. According to Hobbs and Aubry (2007) PMOs’ characteristics could vary significantly that trigger existence of a wide range of PMOs’ types: “The organizational reality surrounding PMOs is complex and varied ... organizations establish a great variety of PMOs to deal with their reality” (Hobbs, Aubry, 2007, p. 85).

Due to the complexity of phenomenon a lot of classifications already exist, however, some types of them seem to be quite similar. In the table below the comparison of some existing classifications is provided.

Table 3: Typology of PMOs by diffrent authors (Hobbs&Aubry, 2007)

Author	Single-project Entity	Multi-project Entity
Dinsmore P. C., 1999	Autonomous Project Team	Project Support Office	Project Management Center of Excellence	Program management office
Gartner Research Group, 1999		Project Repository	Coach	Enterprise
Crawford, 2010	Project Control Office	Business Unit Project Office	Strategic Project Office
Englund, Graham, & Dinsmore, 2003		Project Support Office	Project Management Center of Excellence	Program management office
Kendall & Rollins, 2003		Project Repository	Coach	Enterprise PMO	Deliver Now
Hill, G.M., 2004	Project Office	Basic PMO	Standard PMO	Advanced PMO	Center of Excellence
Garfein, 2005	Project Office	Basic PMO	Mature PMO	Enterprise PMO