The rival cinema chain operators have formed a 50:50 joint venture called Digital Cinema Media to run Carlton Screen Advertising.
The sale comes three months after CSA approached Cineworld with a proposal to renegotiate its contract with the cinema outlet.
As part of the terms of the sale, Cineworld has agreed to terminate the contract, having received full payment from CSA for January and February.
Steve Wiener, the chief executive of Cineworld, said: "DCM plans to develop a more flexible, targeted and timely service for advertisers and local businesses, who hitherto have not been able to make full use of advertising across the cinema sector.
"I believe this will not only be attractive to us but also for other cinema exhibitors that wish to take advantage of DCM's advanced service offering. With the growth potential of digital advertising we believe the prospects for DCM are highly attractive."
In a letter to media agency contacts, Adam Mills, sales director at CSA, said: "This is positive news for CSA as firstly it will put our contracts with major exhibitors onto a more equitable footing and secondly, both Odeon and Cineworld are committed to providing a strong boost to the cinema advertising market by pledging to accelerate the roll-out of digital screens."
CSA has been operating at a loss, having been locked into advertising commitments it made with cinema outlets more than two years ago.
Since signing the deals, CSA and its main rival Pearl & Dean have struggled to make a profit amid a tough advertising climate and aggressive bidding between the two competitors for contracts.
However, despite recent struggles there is widespread optimism in the market about the future of cinema advertising, based on an ongoing resurgence in cinema attendance.
A slew of blockbuster Hollywood movies last summer, including 'Harry Potter and the Order of the Phoenix' and 'Shrek the Third', pushed cinema admissions to their highest level since records began in the 1960s.
The increase in the popularity of the cinema was borne out by figures released by Nielsen Media Research, which showed cinema ad spend increased by 10% on a year-on-year basis to £170m in 2007.
CSA has also attracted new advertisers to the medium, including Apple, John Lewis, eBay and Ford.
The sale follows yesterday's announcement of disappointing results at ITV, as pre-tax profits fell 35% to £188m.
The broadcaster also announced that it had sold its 50% share in Liverpool football club's website for £15.8m to the club.
The disposal of the website and CSA come as ITV sets about reviving its performance by focusing on core assets.
The UK Top 10 films at the box office 2007
1. 'Harry Potter and the Order of the Phoenix', Warner Bros, £49.42m
2. 'Pirates of the Caribbean: At World's End', Walt Disney, £42.23m
3. 'Shrek the Third', Paramount Pictures, £38.62m
4. 'The Simpsons Movie', 20th Fox, £38.54m
5. 'Spider-man 3', Sony Pictures, £33.54m
6. 'Ratatouille', Walt Disney, £24.71m
7. 'The Bourne Ultimatum', Universal Pictures, £23.70m
8. 'Transformers', Paramount Pictures, £22.86m
9. 'Mr Bean's Holiday', Universal Pictures, £22.14m
10. Hot Fuzz', Universal Pictures, £21.0m