Whether your kids are 5 or 25, the holidays stir up some ghosts of Christmas past. All those old toys - now crammed into the closet and under the bed - represent cherished memories.

But could they also represent future treasure? How can you know which are the pop-culture keepers that will be eagerly bought and sold by tomorrow's collectibles enthusiasts, and which will go for pennies at the church rummage sale?

At our house, Star Wars figures and G.I. Joe have set up their operations in tidy storage bins. But Legoland still lives under the bed, a ruined city not unlike Will Smith's New York in I Am Legend.

Before we have a family cleanup, I asked some experts which are important toys of the last 20 years or so, and why.

Nostalgia fuels collectibility, says Alex Winter, general manager of Hake's Americana & Collectibles in York.

"The big hits of the '80s are now being collected because those kids have grown up and their parents have thrown that stuff out. They want to get those toys again."

Today's important collectibles, Winter says, include the small-scale G.I. Joe figures made after 1982 and Star Wars action figures, particularly characters from The Empire Strikes Back (released in 1980) and Return of the Jedi (released in '83).

This year's long-awaited Transformers movie was very much geared to twentysomething fans who played with the toys in the 1980s. Not surprisingly, Winter says, "those items have really taken off in recent years. Mint-in-box [condition] is preferred and brings bigger prices, but even loose Transformer toys have value."

"Unlike a lot of stuff in the 1980s that people went out and bought hoping it would be worth something, I don't think that really happened that much with Transformers. Most people bought those for the kids, and the kids played with them, so mint-in-box Transformers stuff is scarcer than most '80s toys."

Hake's auction catalogs focus on toys from the 1930s through the 1960s, with a few limited-edition pieces from later decades. Where do people buy and sell toys from the 1980s to the present?

"It's a very hotly collected area, but much of it's being done on eBay rather than through auction companies," Winter says. "Those people are young, hip, know what they're doing on eBay, and have cut out the middleman to do it direct. Those collectors like to get together at conventions and do their own Internet thing."

A quick look at eBay turns up more than 8,000 G.I. Joe entries, 13,000-plus Transformers, and more than 27,000 Star Wars-related pieces. In all cases, the toys offered range from "vintage" items 10, 20 or even 30 years old (in the case of Star Wars stuff) to brand new. Many of the toys fall into the 99-cent category, but some lots are in the $100-$300 range and getting dozens of bids.

Explore a little further online and you'll find Web sites geared to specific toy-collecting interests. For example, the Star Wars Collectors Archive (www.theswca.com) makes me glad I held onto the Hoth Ice Planet Adventure Set (circa 1980) and the Ewok Village Action Playset (1983).

All toys are welcome at Geppi's Entertainment Museum in Baltimore, from 19th-century antiques to Strawberry Shortcake, Cabbage Patch dolls, Charlie's Angels figures, and Buzz Lightyear. The museum's curator, Arnold T. Blumberg, is the author of Pop Culture With Character (Gemstone Publishing, $24.95), which has good chapters on G.I. Joe and Star Wars figures.

"There is a G.I. Joe movie in development now. It's being based very strongly on the character names and general layout of the 1980s lines of figures," Blumberg says. "Everything is targeted to the '80s right now. It's inevitable - the slow rolling forward of nostalgia."

Toy nostalgia also has influenced "what the target demographic would be for all basic advertising," he says. "Right around the time the Transformers movie was coming out, they had a lot of new-car commercials. One had a car transform from a metal tiger. . . . It's made for all of us that grew up playing with Transformers - now, they want us to buy cars."

Blumberg, 36, says his generation - the children of the baby boomers - was encouraged "to let go of the notion that there is a line dividing childhood and adulthood."

"Personally, I think that's much more positive than negative. Marketing to adults these days is really just the same marketing you use for children. You evoke all these memories of the toys you played with and the characters you liked."

As it happens, Blumberg says, "I started buying Legos again recently. They're some of the most versatile toys ever. As I've gotten older, almost every year, I always try to get a Lego set or two, to try and stay connected to it.

"Apparently, people around my age are calling themselves AFOL - Adult Fans of Lego. This has been going on for a long time and has become a cohesive, powerful community of adult fans who continue to buy and build Lego, construct their own layouts, and do things beyond the plans on the box."

Bricklink.com offers both an Internet meeting ground and a place where adult Lego architects can find what they need to complete a project.

Blumberg notes that Lego is approaching its 50th anniversary. He hopes to have an exhibition at the museum to celebrate that longevity.

"Antiques" appears monthly in The Inquirer. Read Karla Albertson's recent work at http://go.philly.com/kleinalbertson.