Forrester examined the advantages and disadvantages of large IT departments (defined as those having more than 800 staff), outlining their typical weaknesses and how their performance could be improved.
Advantages of large IT departments include having a well-established management structure and specialist skills. Disadvantages include a geographically scattered business and having to manage complex links between business units and IT systems.
Forrester examined three large IT departments: at an insurance company, an international media company and a government agency.
The media firm's IT department had no properly integrated IT systems following company acquisitions stretching back 10 years. Another problem was that the chief information officer had too many managers to oversee.
"The corporate CIO has 17 direct reports - managing both subordinates and business leaders was too much," said Marc Cecere, author of the Forrester report, The Structure of IT: Large Shop Case Studies. "So this CIO took a hands-off attitude to managing his direct reports and focused more on managing peers and superiors.
"But this limited his ability to make dramatic changes, particularly those that would be threatening to powerful and savvy divisional CIOs."
To improve the performance of the IT department Forrester recommended the media company clarified the IT responsibilities of the CIO and business unit heads. Typically business unit heads are responsible for funding and prioritising IT projects and CIOs are responsible for executing them. Forrester added that the number of people reporting directly to the CIO should fall to between six and 10.