When Piedmont Airlines decided to move its midatlantic reservation center to Reston two years ago, it offered reservationists already working for the company the opportunity to take a job in the new office.

But for at least one reservationist from Winston-Salem, N.C., who asked not to be named, housing in Reston was just too expensive, and she decided instead to stay where she was.

According to employment professionals who worked with people seeking jobs in the new Piedmont office, few of Piedmont's employes took advantage of the opportunity to move to Reston, and, for many of them, housing costs were the reason.

For Reston, a planned town based on the concept of providing an environment where people could live and work without leaving the community, the growth of high-technology industries in western Fairfax County has created a gap between who works in Reston and who can afford to live there.

The firms that have moved to Reston recently, including Sperry Systems Management, GTE Business Communications Systems Inc. and American Telephone and Telegraph, have brought in a large number of clerical-level jobs that pay between about $12,000 and $16,000 a year, said Anne Page, owner of Page Business Schools in Reston. And Reston does not provide enough moderately priced housing to allow many of their employes to live there.

Linda Hill, director of the school, said that Page recently expanded its program because a large number of people from eastern Loudoun, Herndon and Prince William counties want to train for placement in Reston firms.

"Many of the people filling these jobs cannot afford to move here," said Hill. "I suspect many just stay where they are and commute into Reston."

Although Northern Virginia real estate brokers traditionally have considered housing in Reston underpriced, figures compiled by Robert Howard of Wellborn Real Estate show that the resale prices of homes in Reston rose by 8 percent last year and 7 percent in the first quarter of this year, indicating that Reston may be closing the gap with the surrounding housing market.

Last year, the average town house cost $87,100; and the average condominium, $56,000.

"It's probably unfair to just single out Reston," said Deirdre Coyne, spokeman for the Fairfax County Redevelopment and Housing Authority. "For low- and moderate-income families, there is a shortage of available housing throughout western Fairfax, partly because there is mostly only new construction out there."

Spokesmen for firms moving to Reston say they offer jobs at all skill levels and that they often hire for clerical jobs women who are providing second incomes, women seeking to re-enter the workplace after years at home caring for a family.

But even for two-income families, Reston may be too expensive, especially for a family moving in from outside the Washington area.

"Most couples now are making the choice to relocate as a joint decision rather than just depend on one job," said Page. "Many people come to me to find out what kind of salary the wife or other spouse could expect to get in Reston before deciding to take a new job here and relocate."

"The problem is not just with Reston," said Ann McCool, a marketing official with Reston Land Corp. "The problem is with the entire metropolitan area. If a family is moving in here from anywhere other than southern California or New York, they will have trouble finding affordable housing."

McCool said, however, that she believes that a low- or moderate-income family could find housing somewhere in the area, possibly in Chantilly or Herndon, two lower-cost communities within commuting distance of Reston.

One factor making Reston a tight housing market for moderate-income families is an apartment vacancy rate that was less than one percent this past month, said McCool.

Coyne, with the Housing Authority, said that a single parent with one child and with a yearly income of $12,000 a year would be eligible for housing assistance, but added that there is a two-year waiting list for county-owned subsidized housing and long lists at private subsidized housing developments in Reston.

Page said that the trend she has seen among the high-tech firms is for a new company to move its middle-management staff into Reston from other offices, and then hire technical and clerical staff locally. "This means there aren't as many mid-level jobs opening up in Reston anymore," said Page. But it's not just people moving into Reston who find living expenses there high. Page, who has many clients from the Reston area, said that many of them consider a $10,000-a-year job just not worth taking. "They will hold out for a higher-paying job because they say anything less than about $14,000 won't pay their living expenses."