You know the thing about "if it's too good to be true, it probably isn't"?

Well, like every rule, except the golden one, there are exceptions, and here's one: good fat-free pizza. And pretty good "guilt-free" pizza. Let us give thanks for little miracles.

Okay, so it's not a cure for the common cold (although I'm not too sure about that, either), but decent fat-free pizza can lure you into feeling pretty comfortable about breaking your resolutions. Not that a small amount of ordinary pizza is particularly bad for you, as long as you don't pile on those fatty meats, but there's a nice sound to "free." We owe this minor indulgence to Potomac Pizza, a family-owned sub/spaghetti/pizza house whose fourth and newest branch is smack in the middle of the burgeoning Friendship Heights hot-shops area.

(Let's be frank: It's right next to Gifford's ice cream parlor, which brings up a potential conflict, or another reason to save up those fat calories. On the other hand, the menu at all four Potomac Pizza locations is identical -- the others being Potomac Promenade, Traville Village Center in Rockville and Kentlands Market Square in Gaithersburg -- so you can avoid that temptation if you prefer.) Already a neighborhood family favorite, Potomac Pizza is part of a growing resistance against the big chains, which seem to be in competition to offer the most fattening additions and freebies, and is returning to pizza its good name.

Sure, you can get skim milk mozzarella at other places, and a lot of pizzerias make oil-free crusts. But not all come out as tasty and crisp as Potomac's. And you can layer on, as well: When the menu says fresh eggplant, it means it, honorably grilled (and the mushrooms, too, and peppers and so on). The good crust also carries the cheese-less "guilt-free" version, which could be pretty dull. But Potomac Pizza makes lactose-intolerant customers, and the increasing number of children who doctors think may be allergic, feel less like oddballs in the takeout queue. Adorned with fresh tomatoes, broccoli and mushrooms (before you add on), the pizza suggests an open-faced picnic focaccia.

It's nice to be able to report that the subs and sandwiches are equally generous and can be as "green" or low-fat as you like. The grilled tuna for example -- made, like the tuna salad, with "dolphin-safe white meat" -- comes on your choice of whole wheat, rye, pita, tortilla wrap, kaiser or toasted sub, and with its remoulade sauce on the side. There's typical antipasto, but there's also crudites; fried chicken and veal parmigiana but also veggie burgers and roast turkey. Even the frying is done in canola oil, which is about the best you can ask for. "Small" miracles, remember.

* * *

Giuseppi's in Rockville may not advertise its pizza as a healthful item, but it has developed a sort of special-interest style: a low-sodium crust and a tomato sauce that tastes pretty low-salt as well. That rather careful pinch makes the dough, which comes up quite nicely puffy and crisped from the hearth, a little less interesting on its own than it might be, but it may be a question of habit: There are those who swear it's just like their New York favorites. And again, if you do add one of those salty meat toppings, you won't notice. (Here's a suggestion: white pizza with fine, crunchy bacon, fresh spinach and fresh tomatoes, like a BLT by the slice.)

Giuseppi's also has a half-baked idea, but one worth remembering: You can get your pizza partly cooked in advance so you can get that hearth-grilled flavor but still have it hot out of your own oven.

In any case, Giuseppi's has survived a test many small family restaurants would not: transplantation by Metro-area redevelopment, and around the repeatedly redeveloped Rockville Metro at that. Its storefront alongside the Regal Cinemas may not have quite the homey appeal of its former digs on North Washington Street, but the family attitude is the same. (Giuseppi's also has a branch in the Kentlands.)

There are outdoor tables and a microphone system so that you can order, go outside to a table and be called in when your order is ready. Be cautious, however: The mike works both ways, so you may not want to spill all your most intimate secrets over the pepperoni. The courthouse is just around the corner.

Potomac Pizza19 Wisconsin Cir., Chevy Chase;

Metro: Friendship Heights

Phone:301-951-1127

Hours:Open Monday-Thursday 11-9, Fridays and Saturdays 11-10, Sundays noon-9

Prices:Appetizers $1.95-$6.95; entrees $7.95-$11.50; subs and pizza $6.45-$20.95

Wheelchair access:Very good