Baidu's shares, up over 75 percent this year, rose 3.4 percent to $232.60 in after-hours trading on the Nasdaq Stock Exchange. The firm announced its results after the market closed on Monday in the U.S.

Baidu reported a net profit of 181.1 million yuan, up 23.5 percent from a year earlier but down from 288.7 million yuan in the previous quarter.

Baidu expects the "Phoenix Nest" ad system it launched this month to boost long-term revenue despite an initial negative effect on sales, Robin Li, Baidu's CEO, said on the call. Ad providers who upgrade to the new system will gain more keyword options and better monitoring of their ad results, he said. The system will also improve keyword matching for search users.

Baidu this month also launched what is billed as a search tool for the "hidden Web." The platform, called Aladdin, lets users give Baidu descriptions of unstructured items like tables or charts for inclusion in search results.

Baidu also hopes to work with China's carriers on mobile search, Robin Li said. The country's major carriers plan to expand mobile services as they roll out next-generation networks this year.