CHICAGO (AP) _ Michael Jordan is easy to find, the Art Institute of Chicago a little harder. You might get lucky with McDonald's. But Elvis? Forget it _ harder to spot than he is.

The growing popularity of prepaid telephone cards in the United States has spawned an unusual offshoot: phone card collectibles, and the booming hobby is quickly becoming an obsession for some.

``Every one I get, I lock away in a safe,'' Ameritech Corp. Chairman Richard Notebaert said recently, after distributing his company's commemorative calling card featuring Alexander Graham Bell.

Prepaid phone cards have been around since 1976, when Italian officials introduced them to break thieves of the annoying habit of destroying public phones to steal the change.

It didn't take long for savvy entrepreneurs to recognize other uses for the cards, including collecting demographic data on buyers and turning buyers into collectors.

``These things are beautiful,'' says Steve Eyer, a Mt. Zion dealer. ``Some of them are absolutely marvelous, particularly some of the foreign ones.''

Americans weren't introduced to the fad for more than 10 years after the first cards debuted. Even then, it took years more before the first of the so-called ``smart cards'' that deduct set amounts of money caught on.

Debit card long-distance rang up $75 million in earnings in 1993, according to the Yankee Group, a technology research and investment firm based in Boston. It was an $800 million business last year and is expected to bring in more than $1 billion this year.

Companies outside the phone business have caught on, too. The cards have quickly become important marketing tools _ traveling billboards, if you will. And the glitzier the cards become, the more collectible they are.

``The reason the cards are collectible is that they are forerunners of new money, a whole new form of currency that is making cash obsolete,'' said Victoria Stone of Moneycard Collector magazine. ``The other reason people collect them is because they're pretty.''

There's something for everyone in the prepaid card market _ shots of race cars, movie stars, men in bow ties, even McDonald's fries.

Some of the more collectible cards bear pictures of such stars as Elvis or Marilyn Monroe. Betty Boop has a following. Collectors can get a three-card set of JFK portraits worth $400 apiece.

Or they can get in on the ground floor of Air Jordan taking off. For $9 each, you get the joy of collecting a set of the basketball megastar in action (minus a real NBA uniform, which is licensed to the club). Jordan gets the joy of collecting $1 million for giving his image to LDSS World Com, the nation's fourth-largest long-distance provider. Consumers get five minutes airtime on the telephone, if collecting isn't their thing.

Phone companies are reluctant to admit they might issue cards for collectible value, but many go to elaborate lengths for specific artwork and often issue the cards in limited amounts _ a must if the card is to become collectible.

LDSS World Com has quietly grown into the fourth-largest American long-distance phone company largely by selling prepaid phone cards. It issued 400 signed cards in April 1994 of Houston Oilers quarterback Warren Moon shortly before he left for Minnesota, and few of the cards were used for calling.

``Every card that is ever produced has been designed to catch of attention of consumers,'' said LDSS spokesman Chris Schein. ``A benefit of that is the fact that many of them do become collectors' items.''

And while some phone company executives might see the artistic value in producing lovely-looking cards, more are probably looking at the bottom line.

Customers pay as much as $100 for prepaid cards, but they must never use them if they want to increase the value of the card through collecting.

An AT&T card issued for the 1992 Democratic National Convention in New York might get you $1,200 today if you never used it. Used cards might fetch half the price.

Even the U.S. Postal Service, an institution not known for innovation, jumped into into the act last January, when it began testing its own prepaid phone cards in eight cities.

For those who think the fad may fade, take note: The American Numismatic Association (the coin and money collectible people) has brought prepaid phone cards into the numismatic fold.

``There was never a question in our minds that they would not be numismatic items,'' said spokesman Stephen Bobbitt. ``It's basically because a calling card is money, much the same as coins, paper money, tokens and stock certificates.

``The producers of these have created their own little marketplace, something for us to enjoy and collect.''