The charity has handed a year-long account to word-of-mouth specialist 1000heads, to put together and implement an overarching social media strategy.
'We are currently very active on social media and have used it to run successful campaigns,' said CRUK's head of online marketing Michael Docherty. 'But we do not have an overarching way of making the whole more than the sum of its parts.'
He added: '1000heads will help us unleash the broader potential of social media, which we think provides a huge opportunity to get in front of people and deliver word-of-mouth campaigns.'
The charity has already been using social media to reach a younger audience. It launched the Skindividual campaign with Unity to get skin cancer messages across to young people.
It also launched a T-shirt design competition on MySpace to raise awareness of breast cancer.
In total, more than one million people a month visit CRUK's websites, including CancerHelp, the CRUK homepage and Race for Life.
CRUK joins other charities that have revamped their digital comms in the past few months. Oxfam recently appointed its first head of digital comms to overhaul its online activity and Shelter hired a senior Freud consultant to help transform its e-campaigning activity.