Chalet, who has been with CSA since its creation in 1996, is reported not to have a new position to go to.
Matthew Kearney, the chief executive of the North American cinema sales operation Screenvision, is being tipped as her replacement.
Chalet's departure follows a difficult year for the cinema advertising market, which is expected to announce an ad revenue decline on the back of sliding admissions. CSA controls more than 60% of the £188m cinema ad market, with its main rival, Pearl & Dean, responsible for the majority of the remaining market.
The increasing power of a small group of cinema chains that demand ever-greater levels of guarantees from the cinema sales houses has also put increased pressure on CSA.
Earlier this year, it won the contract to sell for Empire Cinemas, and last year it won the Cineworld contract.
Chalet, who is also the president of the Cinema Advertising Association, joined CSA from Carlton TV as the sales director when it was created, following Carlton's acquisition of Cinema Media in 1996. She was promoted to the role of managing director and then to chief executive, before being linked with a management buyout bid for the sales house after the Carlton/Granada merger. Reports at the time valued CSA at around £70m. But, despite selling other non-core interests, the newly merged ITV decided to keep control of CSA.
Chalet refused to comment.
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