Paterson, who joined BBH last October, is taking on the role of executive creative director at CHI, where he will be in charge of the creative department.
At BBH, Paterson had overall creative responsibility for the Boddingtons, Castlemaine XXXX and Unilever's Flora accounts.
He will work out his notice in his current role and is likely to leave the agency after Christmas.
In July last year, it was reported that Paterson was joining BBH after nearly 10 years at DDB London.
Most recently, he had been joint creative director at DDB, sharing the job with Jeremy Craigen. The duo scooped some notable awards, including the Press Grand Prix in Cannes for the "cops" ad for Volkswagen.
When Paterson left DDB to go to BBH, Craigen took on sole command of DDB's creative department.
Prior to his nine years at DDB, Paterson was at Y&R.
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