5810 Greenbelt Road, Greenbelt 345-6101 Hours: Lunch, 11:30 a.m. to 2:30 p.m. Tuesday through Friday; dinner, 5 to 10:30 p.m. Tuesday through Sunday. Closed Monday. Prices: Most dinner entrees $8 to $11. Cards: All major credit cards accepted.

Has success spoiled Chef's Secret? No. After several years in business, it's still jammed on weekends, still serving superlative seafood, and still managing to do it at moderate prices.

Although the outside still looks like a cinderblock bunkhouse, the interior is cozy and inviting, with candles, fresh flowers, comfortable seating and good acoustics. Service lately has been slick, smooth and well-coordinated.

One of the best appetizers in the house, and certainly one of the best bargains at $2.95 a dozen, are the mussels mariniere, fresh and plump, in a heavenly sauce of butter, lemon, parsley and garlic. The clams casino are a no-nonsense rendition, with good, fresh clams and a bit of bacon and pepper, unencumbered by an excess of breadcrumbs.

Don't overlook the soups. The best is the fish chowder, a lovely, delicate, homemade vegetable soup with big chunks of whatever fresh fish is handy; we had it with salmon one night, and it was terrific. The clam chowder is flavorful enough, but it's overdosed with flour, and the cream of crabmeat and avocado soup, an occasional special, doesn't have enough punch to offset its richness.

There are some excellent pastas for appetizer-sharing, too. The linguine with white clam sauce has firm, tender pasta, lots of clam, and enough garlic for zip. The fettuccine Alfredo is probably another good bet.

Entrees regularly include about a half dozen fresh fish dishes. We've yet to find a flop in the bunch. Freshness and spit-second timing are the requisites in cooking a fish, and Chef's Secret has the trick mastered. Even grilled swordfish, perhaps the fish most often overcooked in restaurants, was superb here, beautifully meaty and juicy.

Beyond the fish, there are various combinations of shrimp, scallops, clams, mussels and lobster, all fresh and sweet.

A marvelous way to have your fish and your shellfish too is in seafood en papilotte, in which fresh fish chunks are served with mussels, shrimp and scallops in a sauce of tomato, herbs, garlic, wine and olive oil. The whole thing is presented sealed in a dome of aluminum foil -- split by the waiter, the dome yields a puff of steam and a heavenly aroma.

Just as good is the immense bouillabaisse, which adds half a lobster and an ambrosial, garlicky broth to the mixture.

Don't miss the soft-shell crabs when they have them, sauteed in butter, bursting with juice, lightly crisp outside, and served in a wine-herb sauce.

Chef's Secret provides well for non-seafood eaters too. The chicken Kiev, for example, is a remarkably good version, the meat tender and juicy and the coating with an odd but delicious flavor reminiscent of certain oriental dishes.

The ancillary items here have been consistently first-rate. There's a good little salad with the entrees, and impeccably prepared vegetables. The desserts, on the other hand, are mediocre at best. If you crave a sweet after dinner, order a liqueur or some fresh berries, or put some extra sugar in your coffee.