A Chief Information Office should have influence and oversight over all the information technology-related spend in an organization. It is a truly strategic role ensuring the organization develops and maintains its information processing and digital assets in line with the company's business goals. Usually this will encompass multiple business units.
To compare briefly with other key roles, a Chief Technology Officer will typically drive a strategic technical capability for the organization, usually encompassing significant web-based customer and business solutions. An IT Director will typically be a strategic specialist within a larger corporate IT function (headed by a CIO) or responsible for all IT within a smaller business or corporate division.
The roles and use of titles are still evolving in many organizations. The CIO role is however now established as an important strategic role on most boards.