Open for breakfast Monday through Friday 6:30 a.m. to 11 p.m., 7:30 a.m. to noon Saturday, 7:30 a.m. to 10 p.m. Sunday; for brunch Sunday 10 a.m. to 2:30 p.m.; for lunch Monday through Friday 11 a.m. to 2:30 p.m., Saturday noon to 2:30 p.m.; for dinner 5 p.m. to 11 p.m. daily. AE, CB, DC, MC, V. Reservations suggested. Prices: At lunch $4.25 to $9. At dinner appetizers $2 to $7, main dishes $5 to $18, desserts average $2.50. Full dinner with wine, tax and tip $20 to $40 a person.

Inside the grim walls surrounding Stouffer's National Center

Hotel is a small restaurant that looks like a veranda, with

little private booths lighted by cascading chandeliers and

tropical flowers on the laminated tile tables.

The surprise of this pastel dining room is enhanced as you realize the room is not actually tiny, but made to appear so with tables oriented for privacy. The next surprise is that the service is suave and solicitous, nothing to imply there is a large and impersonal hotel chain behind your host. Then there is the astonishment of finding some Scandinavian dishes on a Washington menu.

The restaurant is named Ondine, after the legendary water sprite, and the menu fills out the usual hotel roast beef and burgers with salmon-filled cr.epes suedoise, smorrebrod sandwiches, biff lindstrom and frikadeller. Its Sunday buffet concentrates--though far from exclusively--on herrings and cured salmons.

Brunch is for many hotel dining rooms their finest moment. They have the size and staff to offer an ambitious buffet. At Ondine, brunch starts with a drink--the champagne in a tall flute balancing a strawberry at the edge is the most festive. The coffee is good and strong, the orange juice fresh. The food choices are vast; begin at the cold table, perhaps with a plate of oysters and clams on the half-shell, fresh and briny, with the usual red sauce or a pale creamy dill sauce. Then move to fishes--the highlight of the meal, you will probably find, for there are smoked ones (whitefish, perhaps trout, certainly salmon) and pickled ones (gravlax and herrings, most deliciously in mustard sauce). Interstices on the plate can be filled in with salads of cucumber, Brussels sprouts, red cabbage, mushrooms, potatoes and probably shrimp (the least satisfactory of them). That's the best. Certainly plentiful enough and of sufficient character to recommend a return.

But the buffet goes much farther, on to several more courses that spoil the first impression. The cornucopia of bread yields ordinary stuff. The omelets cooked to order are a great show, for the chef flips them expertly. But they taste greasy rather than buttery. The waffles, also made to order, are better, though instead of the gummy fruit toppings that are alternatives to the syrup (thoughtfully kept warm on the buffet), you'd do better topping them from the fresh fruit bar. Hot dishes are the real downfall. In handsome copper and brass roll-top chafing dishes were dreadful dried out sweetened chicken, exhausted fish in cream, shriveled meat in another cream, greasy and chewy fried clam strips and broccoli that miraculously stayed green and firm.

From the brunch you can learn how to order dinner. The big advantage of dinner is that the service is quite pleasant and helpful, and there is more of it than at brunch. The menu offers an enormous range of prices, so with a main course of Danish meatballs--frikadeller--or ground beef patty seasoned with onions, capers and beets and topped with a fried egg-- biff lindstrom--each at $6, a dinner can be quite inexpensive. The best value, though, is smorrebrod, a platter of three open- faced sandwiches of your choice piled high so that they must be eaten with a fork, at $5.50. With luxuries such as smoked salmon or gravlax, the good pickled herring or baby shrimp, it is a bargain and a rather nice supper.

For a more conventional dinner, you can start with appetizer servings of gravlax, smoked salmon, herring or shrimp in mustard-dill sauce (though you would do better to order the smorrebrod as an appetizer for two). Even better are the hot appetizers; cr.epes suedoise is the best dish we tasted at Ondine, the very thin eggy cr.epes stuffed with a mild filling of salmon and egg, topped with a light dill hollandaise. It was rich, light and attractively glazed. Also delicious were scallops in lobster sauce, the shellfish--including tiny shrimp--plump and juicy, the brown sauce highly peppered.

Main dishes are shakier. There are sandwiches and burgers plus "traditional favorites" such as steak, roast beef, fish of the day, chicken breast, and shrimp with scallops. I was more interested in the seven "Danish specialties," though not many of them left me interested after I tasted them. Biff lindstrom is a safe choice, for the capers and onions give the lean beef (which is cooked rare if requested) added punch, and the beets are a nice mellow touch. The worst main dishes were the most expensive: prettily presented lamb chops that were dry and chewy, with neither the aquavit marinade nor the herbs coming across ($18); and veal Oscar made with good veal that was overfloured and overpounded, then overcooked and topped with chewy lobster, shriveling asparagus and an undistinguised sauce choron. The ingredients were of high quality--including the vegetables--but nothing spoke Danish.

The wine list--pedestrian choices at Rolls-Royce prices-- tempt one to investigate the Danish beers.

So like most hotel dining rooms, Ondine can be depended on for a show of lavishness; like too few hotel dining rooms it makes a couple of unusual and distinctively good dishes and serves with a zestful and flexible staff; and like even fewer hotel dining rooms it offers, besides extravagances, some dinners priced at the level of a neighborhood cafe.