I'M HOLDING MY BREATH on this one. Boccaccio has the elements of a fine restaurant, and I have happened on some extraordinary cooking there. But I have had to weed out a lot of disappointments to enjoy it.

This is an Italian restaurant by way of Brazil, where the owners have four other restaurants. Like their northern Italian restaurant by the same name in the center of Sao Paolo, this one is decorated with postmodern interpretations of 18th century pillars and archways, finished with hand- painted false marble. The space is generous, the details are luxurious, and while the tone is certainly elegant, it looks as if a couple of decorators couldn't quite agree. Besides that, the chairs are oddly high and unexpectedly hard, despite their soft and cushioned appearance. To its credit, the space is allocated so that there seems not to be a bad table in the house.

As for the cooking, I have hopes. But at $17.50 to $26 for main dishes at dinner and $17.50 to $20 for pastas, hopes are too expensive.

But I'll tell you why I have hopes: A savarin of fish one day had the most extraordinary sauce, a light and translucent pool of riesling-flavored beurre blanc that was so light I wouldn't have identified it as a butter sauce. Its flavor was a delight: The sweetness of the wine was balanced by tartness, with a crunch of minced parsley and shallots and a pungent finish from pink peppercorns. Another reason for hope triumphing over experience was paglia e fieno of yellow and green noodles with broccoli, vodka, tomato and cream. It was also unusual in its interplay of gentle creaminess and peppery, alcoholic sharpness -- a stunner of a sauce. Another pasta was a tour de force in its construction -- pasta squares imbedded with an arugula leaf so they looked like that Japanese rice paper with leaves in it, enclosing duck, porcini mushrooms and foie gras (though it looked more exciting than it tasted).

Appearance is a strong focus for this kitchen. The mousse of prosciutto, quail and mushrooms, a lovely combination of flavors in a soft-spreading texture, is surrounded by paper- thin cucumber slices and tiny cubes of two-color peppers; it must take as long to decorate as to make the mousse. Several dishes have been garnished with tomato roses, yellow ones as well as red ones.

And some of the extra touches raise Boccaccio from the crowd: The bread sticks, long and thin and marbled with herbs, are exceptional. And the bread basket includes wonderful surprises in dark and light breads or rolls in unexpected shapes. After dinner a plate of chocolate truffles, or crunchy meringues, is likely to accompany coffee.

Still, those accessories don't compensate for basic flaws in much of the cooking. And it would be nice if there were an accessory on the plate; main dishes come without a shard of vegetable, and ordering $8 for two.

At one lunch the flaws were chewy, tasteless tuna and veal medallions leached of flavor as if they had been steamed. At dinner the partridge was chewy and gamey with a sauce too intense and heavy. Another lunch showed scallops barely cooked but devoid of flavor; furthermore, they were bathed in a sauce whose only character was an excess of saffron, which left an acrid taste and made one mourn the wasteful expense. Another day black pasta was topped with scallops and salmon of equal blandness. Duck breast, cooked rare and sauced with black olives, came close to delighting, but the olives were in excess and overwhelmed the meat.

It was often a case of mismatching; shrimp were nice enough, and julienned prosciutto contrasted well with them, but their creamy pale sauce tasted like something to mate with meat rather than seafood. Medallions of lobster seemed randomly combined with a pink champagne sauce and caviar; certainly they had nothing in common. And cold lobster, certainly fine in itself, did battle with red pepper pur,ee. Meat sauces were heavy in flavor and thick in texture, and rarely did a sauce seem in accord with what it was meant to enhance. It is perhaps a matter of excess -- excessive reduction, excessive flavoring, excessive thickening, even an excess of fontina cheese on an otherwise delicate and beautifully made pasta roll called anelli di vitello.

Other dishes were just forgettable. A salad of tiny green beans and squid was dressed with no particular distinction, a tagliatelle with asparagus puree wore a plain creamy green sauce that was subtle or bland, depending on your viewpoint; gnocchi with gorgonzola and pine nuts was nice but hardly worth a return trip. Carpaccio was flawless -- perfect paper-thin slices of lean raw beef decorated with parmesan wedges and dressed with a lemony truffle vinaigrette -- but it was not more than you ought to expect at $14 a portion.

Desserts roll by on a cart like a Milan fashion show, but they, too, run the gamut from sensational to indifferent, with more of the latter. On the upper end was a dark and richly flavored chocolate torte with a nutty filling; somewhat less splendid was a zuccotto -- creamy and nutted inside, wrapped in chocolate and vanilla sponge cake. Tiny tarts have been heavy and soggy, ricotta cheesecake was tasteless, and tirami su, the fashionable mascarpone cream custard with cake layers and chocolate, was a fluff of unexciting cream.

So Washington has another grand Italian restaurant, with a dining room staff too numerous to count and a menu that reads like a best seller. It has another lush dining room where you can find a $20 pasta. But does it have another wonderful place to eat? Not yet.