Yahoo is overhauling the way it sells advertising in the US in an effort to help revive the business.
Yahoo derives 80% of its sales from advertising
The internet firm, whose boss Terry Semel quit this month after recent poor trading, is merging its display and web search advertising operations.
The firm's most senior US advertising executive has also left the business.
Hugely reliant on advertising for its revenues, Yahoo said the shake-up would better position it to sell ads across different formats.
A week ago co-founder Jerry Yang replaced Mr Semel as chief executive at a difficult time for the business, which has more than 500 million users worldwide.
Yahoo has lost ground to chief rival Google and has been slow to react the increased popularity of social networking sites.
The firm suffered a sharp fall in profits in the first quarter and said recently that weak display ad revenues would impact on second quarter results.
The overhaul of its domestic ad operation will see greater emphasis on multi-platform selling, encompassing video as well as traditional banner and web search ads.
As a result, chief US sales officer Wenda Harris-Millard is to leave the company and will join Martha Stewart Living Omnimedia.
She said her departure was "not a comment" on Yahoo's recent problems but a reflection of her desire for a new challenge.
The new combined advertising function will be led by senior executive David Karnstedt.
"When combined, the two organisations will deliver profoundly better results than when delivered separately," said Gregory Coleman, Yahoo's executive vice president of global sales.