The summit with Bush, expected to cover trade and moves to avert nuclear advances in North Korea and Iran, was also likely to touch on intellectual property. U.S. industry groups estimate 90 percent of DVDs, music CDs and software sold in China are pirated.
After the meeting with Gates at Microsoft's headquarters, Hu reiterated that China would move against software pirates.
"China is focused on and has already accomplished much in creating and enforcing laws to protect intellectual property," he said. "We take our promises very seriously."
After the meeting, Hu was invited for dinner at Gates' $100 million lakeside mansion with about 100 other guests.
China's Ministry of Information Industry, which regulates the technology sector, has recently begun requiring Chinese computer makers to preload legal software on their machines. It is not clear how well that order, which was issued just this month, is being enforced.
In Seattle, advocates of various causes protested near the stately Fairmont Hotel where the Chinese president was staying. They included supporters of the Falun Gong spiritual movement, which is banned in China, some demanding China get out of Tibet and others asking China to let Taiwan become independent.
In Seattle's Chinatown, many stores hung Chinese and U.S. flags to welcome Hu, and many in the crowd outside the hotel were there to support the Chinese president, or simply curious about all the fuss.
In Washington, D.C., on Thursday, Hu will lunch at the White House where Bush said he would bring up Iran's nuclear program. Bush wants China to agree to more pressure on Tehran through the U.N. Security Council, something Beijing is resisting.
"I intend of course to bring the subject up of Iranian ambitions to have a nuclear weapon," Bush said on Tuesday. "We'll continue to work diplomatically to get this problem solved." Iran says its program is just for nuclear energy.
Before the visit, China sought to quell U.S. trade complaints by signing contracts worth $16.2 billion while Vice Premier Wu Yi visited the United States last week.
Bush, visiting a school in a Washington, D.C., suburb, said China was both a partner and competitor.
"We can either look at China and say, let's compete with China in a fair way, or say, we can't compete with China and therefore kind of isolate ourselves from the world. I've chosen the former route for the United States," the president said.
But U.S. Deputy Secretary of State Robert Zoellick said Beijing had been "agonizingly slow" in meeting U.S. demands to reform its currency. U.S. officials say the yuan is undervalued, making Chinese exports artificially cheap.
The U.S. trade deficit with China totaled $202 billion last year.
Hu also wants Bush to offer some assurance that the United States will restrain Taiwan's independence-leaning President Chen Shui-bian, Chinese analysts said. Beijing says the self-ruled island must accept reunification with the mainland after over half a century of separation.
Before leaving Seattle on Wednesday, Hu will visit Boeing. Shortly before his visit, China signed a deal with the company to buy 80 737 jets worth around $4 billion.