Barbara Bush raced past the mistletoe, "afraid you might think you had to kiss me," she teased the media, decked out in the usual stakeout garb for a day in the life of the White House. But then came a surprise that even her staff didn't know about -- a peek at the family quarters, spruced up for the holidays.

"Let me tell you," the First Lady began yesterday after winding up her guided tour of the mansion's Christmas finery, "because the president has someone coming to lunch, I haven't invited you upstairs. But I can invite you if you can literally run upstairs, down the hall and be out in 15 minutes."

Could they ever. Some in the group of 40 or so, like ABC correspondent Ann Compton, who has been covering the White House for 17 years, had never been beyond the public floors. And UPI correspondent Helen Thomas called the impromptu Christmas tour a "first" in her many years of covering presidents.

So everybody climbed the same Grand Staircase that presidents and kings use, and learned a few things on the way. One was about the night the Bushes escorted Hungarian Prime Minister Jozsef Antall and his wife up the staircase, only to find the door at the top locked.

Yesterday, the door was open, revealing a suite of rooms filled with the homey touches of a big and active family, from grandchildren's stuffed animals to holiday mementos, including a needlepoint creche from the First Lady's Houston church.

There was an unceremonious air about the usually formal Yellow Oval Room, where oversize Christmas stockings bearing children's names were hung by the ornate fireplace, and well-thumbed children's books lay on a coffee table. Centered in the window overlooking the Truman Balcony was a 16-foot-tall Fraser fir laden with ornaments, some given to Mrs. Bush by her mother, others made by the Bush children years ago. The tree, like other decorations throughout the mansion, went up on Friday while Mrs. Bush was at Camp David.

"When I came back," said Mrs. Bush, grinning mischievously, "it was done. Was I mad!"

An estimated 100,000 visitors will tour the White House during the holiday season, inspecting a dazzling production totaling 47 Christmas trees, including one in the Oval Office decorated with homemade cookies. ("I never ask," the First Lady said when asked who eats the ornaments.) There are 54,000 lights on those trees, according to Mrs. Bush, of which 6,000 glow on the official tree in the Blue Room.

That 18 1/2-foot-tall Fraser fir is heaped with hundreds of ornaments, many handmade by the White House staff to carry out this year's "Nutcracker" theme. "Everybody in the White House had a part in it," said Mrs. Bush, pointing out some of the 45 porcelain figures representing dancers from Tchaikovsky's ballet, 50 pairs of ballet slippers (including one pair bearing Bolshoi signatures, given to her last summer) and hundreds of velvet balls and hand-blown glass ornaments dating back to the Eisenhower administration.

"I didn't do anything except admire. You know, Will Rogers used to say, 'Some people can sit on the curb and clap as the heroes go by,' " she said.

Lush garlands of greenery, perky poinsettias and fat red ribbons were everywhere. In the State Dining Room, for the 21st consecutive year, Executive Chef Hans Raffert presided over his gingerbread house, a creation he baked and built during a 24-hour period and that this year incorporates "Millie's House" and a miniature Millie, taking it lying down.

If the real Millie, splendid in red bow tie and also taking it lying down, didn't seem particularly impressed, her mistress did. She realized then why no one would allow her near the State Dining Room during the weekend.

The First Lady told how her grandchildren had a "snowball" fight using artificial snow when the White House staff and 40 volunteers from the florist industry started to dust the trees. And she said President Bush "visited with the volunteers" before going upstairs to the family quarters after arriving home from South America Saturday night.

She said she "bothered them" off and on during the weekend because she "could hardly wait to see what had changed." And she is so eager for others to see the White House decorations that she wishes there were a way they could be displayed in other U.S. cities.

The Bushes' Christmas plans include observing the holiday at Camp David and attending church services there. Asked about Pentagon restrictions on Christmas observances by U.S. troops in Saudi Arabia, the First Lady said it is "too bad. ... But you know, when in Rome, I guess you have to do what the Romans do. ... But it doesn't stop the heart from beating with your religious beliefs."

She said an aide took care of her Christmas shopping and kidded her for being "extravagant" when it came to buying gifts for her grandchildren. As for herself, she said, the only thing she wants for Christmas is "peace."

"I have way too much in life, as does George Bush," she said. Even so, she is going to give him something he "needs," but she refused to say what it is.