Sometimes referred to as Silicon Alley, owing to its purported small size, New York’s high technology sector has seldom been seen as a major player.

But a nonprofit group hopes to challenge that perception when it releases a report, due out tomorrow, that says that New York has more high technology workers than innovation meccas like Seattle, or even Silicon Valley itself.

The report, “Buried Treasure: New York’s Hidden Tech Sector,” counts tech workers at major companies that have offshoots in Manhattan — such as Microsoft, IBM and Google — as well as those who work at research and development departments at medical institutes and other organizations.

“This is not a city where you drive down the street and see buildings with technology firms’ names on them,” said the president of the Industrial Assistance Corporation, Sara Garretson. The IAC is a nonprofit economic development organization that commissioned the study.

Based on the authors’ unique accounting, the New York Metropolitan Statistical Area that covers southern New York and Northern New Jersey has nearly 620,000 technology workers. That is more than twice the number of such workers in Silicon Valley.

By contrast, Popular Science magazine in 2005 rated New York 39th among high-tech cities.

The new study looked at more than 180 companies that rely heavily on technology. It also recommends creating an Office of Science and Technology Enterprises within the mayor’s office and starting a “branding” effort to attract talent and financing for startups.

The chief executive of Joint Venture: Silicon Valley Network, a nonprofit regional planning group in San Jose, Calif., Russell Hancock, questioned whether such initiatives would stoke growth in New York’s high-tech sector.

“Place still matters,” he said. “What’s in the Silicon Valley is a critical mass, just this dense, fibrous network of innovators, of technology people bumping into each other like molecules in a gas.”