Under the terms of the deal the washroom specialist will provide support for all Missing People's campaigns throughout 2010 by offering the charity media space.
The partnership follows an initial campaign which a spokesman for Admedia said was the most successful integrated marketing promotion ever for Missing People and secured more than 600 new text donors.
Adam Mills, managing director of Admedia, said there is a "natural synergy" between Missing People's objectives and the type of media Admedia offers.
Mills said: "Our A3 panels offer long dwell times which is vitally important when trying to jog someone's memory and offer real impact and standout. It's a totally unique time when consumers have the time and patience to read an ad and we believe our partnership will offer genuine help to find those who are missing."
As part of the partnership Admedia will also engage its staff with fundraising and volunteering opportunities for Missing People.
A team from the outdoor media owner will run the Milton Keynes half marathon for the charity and a separate team will run Missing People's first ever in-house running event 'Miles for Missing People'.