3116 M St. NW., 342-1854. Open from 11:30 a.m. to 11 p.m. Sunday through Thursday, until 1 a.m. Friday and Saturday. Reservations suggested. AE, V, MC, Choice. Prices: Appetizers $2.50 to $4, salads and sandwiches $4.50 to $6.25, dinner entrees $6.50 to about $12, desserts $2.50 to $3.50. Full dinner with wine, tax and tip about $25.

HERE IS WHAT is meant by a Georgetown garden: a narrow but pretty little oasis enclosed by high brick walls and shaded by an ancient tree. And Lisa's cafe goes a few steps further: in its long, two-level garden those brick walls and a wood fence are covered with grapevines, and tables are covered by vinyl cloths splashed with bright flowers. The cacophony of Georgetown is drowned out by gentle bird sounds.

The inside of Lisa's, newly refurbished, is also an example of Georgetown at its most charming. Windows in front, a large arched window in back and a skylight intensify the bright, sunny look. This is a restaurant for casual dining, its wood tables bare and its decorations earthy pottery on mirrored walls and baskets massed with tiny dried flowers.

Between these two environments, though, the mood is disrupted by a dingy mess of a hallway. Maybe that's to make you appreciate how much had to be done to make this little restaurant so attractive.

The menu has been revamped, too, but it still concentrates more on salads and sandwiches than on dinners. In the evening there are a few specials and the standing menu of three appetizers -- soup, roquefort and red pepper flan, and,e -- plus six main courses of modern-day style -- torta rustica; mussels with linguine; tortellini with pesto cream; chicken with raspberry mustard sauce; sole with hazelnut-dill vinaigrette and baby shrimp; and cold salmon with garlic mayonnaise. You can order sandwiches and salads in the evening as well as at lunch, plus a couple of cold daily specials at lunch. The menu also lists wines, a mere dozen, all Californian, and most very reasonably priced at under $12. What's even nicer is that several of them are available by the glass at equally reasonable prices.

So far, it all sounds promising. And, in fact, what is on the plate is promising -- but not yet achieving.

Although this is a restaurant that emphasizes sandwiches and salads, they have not been nearly as good as the cooked dishes. One evening's special of sliced tenderloin with mushrooms ($12) was quite delicious, the beef -- cooked just as ordered -- tender and flavorful, in a creamy beige sauce that tasted of a mustard tang and a careful sprinkling of herbs. The sole, too, was particularly good, mounded with an unusual and delightful green puree with the crunch of hazelnuts and delicate in its use of vinegar. The fish tasted cleanly fresh and accurately poached. With both those dishes was right green broccoli cooked to a crunch, and disappointingly dull packaged linguine bare of dressing, but improved by swirling in the sauces. Entrees are preceded by a big bright mountain of salad -- dark greens, red onions, cherry tomatoes and such, with a homey creamy vinaigrette on the side.

In addition to those very good cooked dishes I have had an excellent vegetable soup -- firm and sprightly carrots and celery, potatoes with their skin on, highly seasoned and sharply peppered. Its fault, though, was in its naming; the menu called it vegetable soup with mussels, but two mussels were barely enough to consider plural. The roquefort and red pepper flan is also a fine appetizer, a wedge of subtle and intriguing melding of flavors -- a sort of crustless quiche. And gazpacho blanco, a prettily translucent white cold soup, was not too different from cucumber soup but nice enough.

The easiest parts of the menu, though, seem hardest for this kitchen to accomplish. Peasant salad sounds just wonderful: marinated new potatoes, julienne ham and swiss cheese, toasted walnuts, a bed of red cabbage and shallot vinaigrette. But the potatoes were undercooked, and not only introduced an unpleasant crunch but also did not absorb the flavor of the dressing. And the ham and cheese were uninteresting, alone and in combination with the salad.

Likewise, a sandwich called Peter's Premonition, which the waiter told us was the customers' favorite, sounded stupendous: smoked turkey and brie in a french toasted sandwich. It was, however, two large thick slabs good close- grained bread with a homemade texture and only the thinnest wash of egg batter so that it

remained dryly intact after its

french-toasting. Furthermore,

there was far from enough filling

for so much bread, and the smoked

turkey was thin, dry and salty. A

daily lunch special of shrimp salad

was indeed nice large shrimp of

good texture, but it had no flavor,

and its underseasoned dressing

tasted like plain yogurt. Five

shrimp and a garnish of tomato

wedges on a leaf of endive made a lunch that wasn't worthy of its setting. Both the salad and the sandwich were ideas worth further refinement, for they were imaginative and close to being successful.

From the moment you walk into Lisa's it is apparent that dessert is considered almost as important as it was when this location was called A Piece of Cake. A glass-fronted counter inside the door displays shelves of tortes, tarts, mousses and brownies. The desserts, even more, lead to high expectations but sometimes dash them through carelessness. Lisa's Dome Cake is a fine job -- dense, dark chocolate Grand Marnier mousse enclosed in a dome of fudgy chocolate glaze and served in a slice under a drift of chantilly cream. One day there was a potentially more interesting chocolate backberry torte, and it would have been terrific if it hadn't been stale. The cake layers were dry and the whipped cream-blackberry filling and frosting had also lost their moistness and much of their flavor. Lemon mousse tart is a pretty little thing, layered with rosettes of whipped cream. Its cookie crust is buttery, though a bit hard, while its filling has a lovely tang. Its only problem is that it is not lemon mousse, but lemon curd -- good, but again misnamed. There is plenty to choose from -- carrot cake, spongecake layered with fruit and cream, chocolate mousse amaretto cheesecake, chocolate mousse pie and brownie topped with ice creeam and fudge sauce, along with daily specials such as apricot-prune bread pudding, which, unfortunately, was dry and chewy as if it were yesterday's special.

Lisa's is an endearing little restaurant, with nice, if unpracticed waiters and a fresh, youthful eagerness. And clearly it has a good cook on the premises. Now that the dining room is refurbished, it is, one hopes, geared up to show the discipline in the kitchen that will add to its imagination some all- important consistency.