Open for lunch Monday through Friday 11:30 a.m. to 2:30 p.m., for dinner Monday through Saturday 5:30 p.m. to 10:30 p.m., Sunday 4 p.m. to 10 p.m. AE, CB, DC, MC, V. Reservations suggested. Prices: at lunch, entrees $6 to $9; at dinner appetizers $6 to $8.50, soups $4 to $4.50, pastas $8 to $9, entrees $11.50 to $14. Full dinner with wine, tax and tip about $30 a person.

From the outside it is just another suburban hotel dining room. But inside, Mamma Regina's has new life as a trattoria in search of a neighborhood. The dim room may not be much changed from the leatherette and brass planters of yore, but the new management has revised the menu and the spirit is that of a family. Where else in Washington do you find the restaurant's off-duty waiters in the lounge poring over cookbooks? In how many restaurants do the wife and children of the management carry on their evening activities in the dining room? How frequently does a diner waiting for a companion sit with the manager and chat until the companion arrives?

One visit and you become part of the Mamma Regina family. Like any family, it has its advantages and its pitfalls.

The new menu has a full page of appetizers, ranging from stuffed eggplant and mushrooms to snails pizzaiola and a page of pastas from ravioli to chocolate fettucine with sausage and parmesan. Thus it is immediately apparent that this is an uncommon Italian restaurant.

The restaurant is now being run by Sergio Toni, who had been at Cantina d'Italia, and he brings with him some of that restaurant's assets and flaws. Mamma Regina serves some outstanding dishes, full of boldness and flair. Mussels float in a pungent strong-flavored and light-textured tomato broth spiked with plenty of red pepper and garlic, and the mussels themselves have been superlative. And among the pastas are some dazzlers, particularly pappardelle alla ammiraglia, wide homemade noodles tossed with juicy seafood-- shrimp, squid and clams--and brashly seasoned with garlic, olive oil and red pepper. An apparently simple green fettucine with fresh mushrooms, garlic, butter and parmesan is extraordinarily suave yet earthy, the mushrooms cooked in butter so they perfume not just the dish but the whole table. Fettucine Roberto is a delicate and subtle blend of toasted pine nuts, cream and parmesan on the kitchen's very good and properly cooked handmade fettucine. So what happened to the pasta with smoked salmon sauce to deprive it of all but the faintest flavor? And why was the hand so heavy with the salt in the carbonara?

Among main dishes, note that a full page--half the possibilities--are veal, and with good reason. The kitchen uses very good veal, cooks it painstakingly and--even more important-- seasons that delicate meat with outstanding sauces. Go no further than the vitello cremoso, veal scaloppine saut,eed with butter and white wine, topped with fresh tomatoes and fontina cheese. The cheese melts into what seems like the richest yet slightly earthy cream sauce, with the tomato acid just what is needed to cut into the richness. For braciole, the veal scallop is rolled around a delicate mushroom p.at,e and a lot of oozing mozzarella, then saut,eed so that the surface is crusty but the meat is not overcooked and stringy. It is topped with a tomato-mushroom cream that seems to be the kitchen's hallmark. It is a fine dish, though one might be tempted to try veal with scallions, mushrooms and "eight different herbs" or with marsala and gorgonzola, with grated lemon and yogurt, or folded around prosciutto, ricotta and spinach. There is even a veal "dieter's delight" with onion, mushrooms, tomato and low-fat yogurt, or its opposition, Scaloppine alla Sergio, which blends bacon, onion, brandy, butter, cream and mushrooms. Beyond scaloppine, the menu lists liver Venetian-style, osso bucco, a couple of beef fillet and chicken breast dishes, two lamb dishes and a half-dozen seafoods.

The problem is grease. Fried mozzarella oozed grease more than cheese. We tried lamb cutlets in a sauce of white vinegar, fresh rosemary, oil, garlic and wine, and the tart herbal sauce was everything we had hoped. But the lamb was inordinately fatty and swam in a pool of grease. Though the members of the dining room staff nearly turn themselves inside out to please, the reply to our complaint on this was simply that's the way the lamb comes. Broiled rockfish with pur,ee of basil, garlic and lemon sauce, too, was of excellent flavor, and the pristinely fresh fish was cooked just right. But it was drowning in butter. Another day the sea trout was far less fresh, and the sauce not only swamped it but was too sharp from insufficiently cooked onions.

So you take a chance at Mamma Regina. If you win, it is a big success, for some dishes will leave you wishing to return the next night. But at prices of $6 or so for appetizers and $13 for main courses, there are too many missteps. As for accompanying flourishes, the bread is a chewy, crusty success but the spinach salad is a dud of just raw spinach and a more or less zesty vinaigrette. Sometimes a vegetable comes and sometimes not, but when it is paper-thin strips of zucchini lost in an inch- thick greasy batter, it might as well not. Desserts are said to be made there, but the "cheesecake" was a dead ringer for frozen chiffon cream pie defrosted days ago. There is a bland caramel custard, zuppa inglese with plenty of rum and too much airy fluff that is called whipped cream, and the prefilled cannoli did not look tempting. The wine list is small and doesn't reveal vintages, which is gutsy with the average bottle hovering around $16.

Mamma Regina is an agreeable restaurant, oozing with concern as well as mozzarella with each course. In an anonymous way, it is comfortable and attractive. And there is excitement on its menu. I wish it had begun with more modesty in its pricing, to give more diners incentive to try it and to warrant more forgiveness for its flaws.