Downtown Seattle was bustling last May, with every hotel room from Lake Union to Safeco Field spilling over with dentists from 80 countries. To create the largest convention in more than a decade, buses shuttled overflow delegates across Lake Washington. Restaurants were booked for days. Kenny G played at Benaroya Hall. The convention bureau estimated that spending by the more than 15,000 delegates produced a local economic impact of $30 million.

The gathering, of the American Association of Orthodontists, was by almost any account a huge success. "Our people always want to come to Seattle," says Don Joondeph, who practices here and was then the association's president.

But they're not coming back.

"We put them in here with a shoehorn," says John Christison, president of the Washington State Convention & Trade Center. "We had issues with, No. 1, the amount of quality hotel rooms. We had to push them all over the region. They told us they loved us, they loved the service, they loved the convention center, but they can't come back."

It's a strange thought, set against the backdrop of construction cranes and scaffolding that sometimes seem to be remaking all of downtown Seattle into a room with a view. And, in fact, if you're a vacationing family, there's probably hotel room to spare here. But from a growing business point of view, there aren't enough rooms at the inns. And not enough meeting space, either.

We're not alone. There is a national, indeed a worldwide, shortage of upper-end hotel rooms -- the kind attractive to luxury and business travelers, The New York Times reported earlier this year. That's spurred higher rates and a building boom, and the Puget Sound area is certainly no exception. The newest lodgings in town, according to Seattle's Convention and Visitors Bureau, are:

• The Silver Cloud Hotel, 210 rooms at Safeco and Qwest fields.  A second tower at the Seattle
• Sheraton, adding 415 rooms and bringing the hotel, the area's largest, to a total of 1,258 rooms.
• The Heathman in Kirkland, with 91 rooms. Coming soon are:
• The Hyatt at Olive 8, 350 rooms near the convention center set to open in January.
• The Arctic Club Hotel, a renovated piece of historic downtown Seattle, with 120 rooms opening this year.
• A second tower next summer at the Hyatt Regency Bellevue, bringing 350 new rooms to the hotel's existing 382.
• The Four Seasons Hotel in Seattle, with 150 rooms opening this fall.
• The Hyatt Place Hotel, with 158 rooms opening this summer at south Lake Union.
• The 1 Hotel & Residences in Seattle, 192 rooms opening late next year.

On the horizon, with an expected arrival date about three years out, is a huge hotel, 51 stories and 1,230 rooms, on the site of downtown Seattle's Greyhound bus station. It doesn't have a name yet, but it will have more than a thousand rooms, and that turns out to be very important.

From a business point of view, one way to divide up hotels is by size and market -- "boutique hotels" versus "big boxes." The definitions aren't precise, but boutique hotels trend smaller and toward branding themselves with special features. A lot of the hotels currently going up are boutiques. "The first test is size; the second would be its character, its facilities and amenities," says Andy Olsen, managing director of The Chambers Group, a hotel consultancy. How do these hotels compete? "It's the style, quality and size of the guest rooms, the spa or fitness facility. Is there a business center? Flat-panel TVs? Think of the Vintage Park, the Sorrento, the Inn at the Market, the Andra. The Hotel 1000 is one of the more, if not the most, wired in the city, with a virtual golf course in the lower level."