Paddy joins the child protection charity on 20 June after four years at Amnesty, latterly as media and audio-visual programme director.
He is tasked with re-establishing ChildLine's profile to the levels it enjoyed in the wake of its launch in 1986, said director of policy and comms Natasha Finlayson.
'Our profile has declined a little because of competition from other children's charities,' she said. 'The likes of the NSPCC and Barnado's have very large budgets for integrated marketing campaigns. We do not have that money, and do not advertise, so having a seasoned media manager is vital.'
Finlayson said Paddy will develop a media relations campaign to support ChildLine's 20th anniversary next year. 'We're particularly interested in reaching opinion formers,' she added.
'We traditionally do well for coverage in the regional and tabloid press. We need to target the Sunday and broadsheet newspapers, as well as the likes of the Today programme and Newsnight. We want to ensure ChildLine is seen as credible, authoritative and a vital piece of the child protection jigsaw.'
'ChildLine is a small charity, reliant on public goodwill. Media and PR activity are crucial to the charity's success,' said Paddy, who replaces Liz North. She left to become head of media at Macmillan Cancer Relief in April.
Paddy has been replaced at Amnesty on an interim basis by freelance consultant Richard Bunting.
The human rights charity hopes to have a permanent replacement by September.