The review followed the appointment of Lesley Miles, previously marketing director at Waterstone's, as the charity's first dedicated communications and marketing director.
Miles has been given the brief to raise awareness of the charity.
The hospital has a fundraising target of £20m this year, and one of Miles's tasks is to devise a strategy that will help the charity double current fundraising revenues by mid-2009.
The money raised will be used as part of an upgrading programme, which aims to redevelop two thirds of the hospital's facilities.
Great Ormond Street has the largest number of children's specialists of any UK hospital, and is the biggest centre for children's heart or brain surgery, and children's cancer care, in the UK.
The charity previously focused its marketing on public relations and direct marketing activity, and works with direct marketing agencies Arc Worldwide and WWAV Rapp Collins London.
Earlier this week, The Metropolitan Police confirmed that MediaCom had retained its £6m media planning and buying account for the next three years. The agency was on a pitch list including Starcom and PHD.