AS of Jan. 1 of this year, manufacturers of wood treated with chromated copper arsenate voluntarily discontinued marketing the product for use in things like children's' play sets, lawn furniture and decks.

And while this may not be a major problem for manufacturers of play sets and lawn furniture -- there are a number of other materials commonly used in such items -- the impact the move had on decks is a bit more noticeable. That is because ''pressure-treated wood,'' as it was generically called, is the material that most homeowners think of when building a deck.

With wood treated with C.C.A., as it is familiarly known, off the market, what is a homeowner who wants to build a deck to do?

''The good news is that today consumers have more choices than ever before when choosing decking materials,'' said Anatole Burkin, editor for decks and outdoor projects for the Taunton Press, a publisher based in Newtown, Conn. ''The bad news is that some of these new choices haven't been around for very long.''

Mr. Burkin said there are a number of chemically treated, natural and synthetic materials to choose from when building new decks.

''I personally like the look of wood,'' he said. ''And if you like the look of wood, you can't replace real wood with something man-made.''

Mr. Burkin said that for those who share his preference, a choice must be made between untreated wood that is naturally resistant to bugs, rot and decay and wood that is chemically treated to exhibit the same qualities.

The most common natural materials used for deck surfaces, Mr. Burkin said, are cedar and redwood. These have been used on the exterior of homes for many years, he said, and they are now a ''known quantity.'' Builders and homeowners are familiar with how they will age, how they will look as they age and how they will hold up to weather.

But a problem with using cedar and redwood, he said, is that they are generally too expensive to be used for parts of the deck that will not be seen. As a result, in most cases, chemically treated southern pine is used for posts, beams and joists that form the substructure for most decks.

Since the use of C.C.A. was discontinued, manufacturers have begun using other chemical compounds to treat wood, including southern pine, that is to be used outdoors and wood that will come in contact with dirt.

Jim Hale, executive director of the Wood Preservative Science Council, an industry organization based in Mount Vernon, Va., said two such compounds are alkaline copper quaternary (A.C.Q.) and copper azole (C.A.). Both compounds, Mr. Hale said, are pesticides approved by the Environmental Protection Agency that resist bugs, mold and rot.

As a result, he said, they can be used for both the structural components of a deck and the walking surface and railing material as well. ''In terms of performance, consumers should see no difference whatsoever,'' Mr. Hale said. ''All the test results we've seen show that the alternative preservatives work just as well as C.C.A.''

But treating lumber with A.C.Q. and C.A. is more expensive than treating it with C.C.A. ''I think consumers are going to find a 10 to 20 percent increase in the cost of the material,'' Mr. Hale said.

Another thing that consumers should be aware of when using lumber treated with A.C.Q. or C.A. is that the hardware used in the past for pressure-treated decks -- typically, galvanized steel -- may not be the best thing to use with the newer preservatives.

Fredy Lowe, the owner of Driscoll Signature Decks in Little Egg Harbor, N.J., (www.driscolldecks.com) said that there is some concern that the chemicals used in A.C.Q. and C.A. will corrode the standard galvanized hardware sold for use with C.C.A.-treated lumber. He said that on the newer treated lumber, the metal fasteners, nails and screws used to hold the deck together should be either stainless steel, double-dipped galvanized or material that has a ''triple zinc coating.''

''Consumers should make sure that the hardware they are buying is rated for A.C.Q. or C.A.,'' Mr. Lowe said.

He noted that while he uses A.C.Q.-treated lumber for the structural elements of most of the decks he builds, he uses synthetic materials for the decking itself. ''I would say that 85 to 90 percent of the new decks I install are made with composite materials,'' he said.

Mr. Burkin of the Taunton Press, said that such decking -- which is manufactured and sold under brand names like Trex (www.trex.com), Nexwood (www.nexwood.com) and TimberTech (www.timbertech.com) -- is generally made of recycled polyethylene and wood fiber.

Another synthetic decking material is made out of polyvinyl chloride. One vinyl deck brand is Dream Deck (www.thermalindustries.com), and another brand name is Brock Deck (www.royalcrownltd.com).

The allure of composite decking, Mr. Burkin said, is that it is splinter-free, maintenance-free, fungi-free and basically impervious to rot and insects. At the same time, he said, ''composites haven't been around long enough to study their performance over the long haul.''

Generally speaking, Mr. Burkin said, the composites are more expensive than chemically treated wood and less expensive than many natural wood decking materials. For example, he said, Trex costs about $1.75 per linear foot for a standard six-inch-wide deck board. A similarly-sized piece of clear western red cedar would cost about $2.35 a linear foot; ipé, a tropical hardwood that makes excellent decking, costs about $2.20 a foot; and redwood costs anywhere from $2.50 a foot to more than $7.50. A six-inch wide board treated with A.C.Q. or C.A., on the other hand, would cost about 80 cents a linear foot.

One reason redwood and western red cedar are relatively expensive on the East Coast is that they generally grow on the other side of the country.

One natural decking material that grows here, however, is northern white cedar.

David Gordon, the owner of Katahdin Forest Products in Oak Field, Me., said the northern white cedar that his company sells is often used in high-end children's play sets. ''It's lighter than pressure-treated decking, easier to handle, splinter-free, and it doesn't contain any chemicals at all,'' Mr. Gordon said.

And while the prices ultimately paid by consumers depend on the availability of the material and shipping costs, it is possible to purchase northern white cedar direct from Katahdin for slightly more than the cost of pressure-treated wood.

Additional information about Katahdin's decking material is available on the company's Web site at www.usaloghomes.com.