hen my son Thomas was seven, he cut open the big, blue plastic piggy bank he'd had since he was two and rolled all the coins. Then we headed to the local bank to open a passbook savings account with his $101.17.

Thomas was proud of his savings and dutifully impressed by the attention given to him by the bank officer, who asked him to sign his name on the line. She confirmed that we'd counted his stash correctly, providing another small lesson. He had even digested my explanation of compounding interest. Sort of. On the way home he asked, "When do they start sending me the money?"

Another milestone. Passbooks can play a critical role in teaching a young child about money. Our bank waives the fee on any account for a child who has at least $1 to deposit. The bankbook is impressive. And keeping track of it requires a sense of responsibility. Still, the exercise left me wondering about passbook accounts. Why have they been around so long? Does anyone else use them?

Lots of people do, as it turns out. There is nearly $1 trillion in passbook accounts or their equivalents today - much more than the $612 billion in money market accounts, which earn a higher rate of interest - according to Sheshunoff Information Services Inc., and they show no sign of dying out. It's even more than the $827 billion stored in all other "timed deposits" of less than $100,000, such as certificates of deposits.

"It's remarkable the way deposits in passbooks have remained steady over the years," says Fritz Elmendorf, a spokesman for the Consumer Banks Association. "Back in the early '80s, passbooks were holding steady even when there was a big difference in interest rates. Now there's not a big difference."

Surely American children don't have that much money. In fact, Elmendorf says the use of passbook accounts cuts across all demographic groups. "It's probably weighted a little bit toward older people," Elmendorf said. "But it really cuts across a broad section of people of all different ages."

But could there be any advantage? I decided to do a little research as I was walking down Fifth Avenue in New York. I headed into the Dime Savings Bank on 48th Street and asked Colett King, a young woman seated at the front desk, about the advantages of a passbook account.

"People like to have a passbook account because it restricts them from using the money," King said. For instance, there's no access to a passbook account with an automated teller machine card. Instead, you must bring your passbook into the bank to deposit and withdraw from the account.

What about interest rates? The Dime pays 2.5 percent interest on passbook accounts - the same as for statement savings accounts. Each also carries a $3 fee for any month that the balance drops below $500. Ouch!

I headed straight across Fifth Avenue to Fleet Bank to see if the bankers there had any additional information. "What's the advantage of a passbook account?" I asked the woman on duty. "Oh, we don't have them anymore," she said.

But Valerie Lee, who worked at the next desk, corrected her. The bank does have passbook accounts, it turns out, but there is clearly no advantage. Both passbook accounts and statement savings accounts at Fleet were paying 1 percent, Lee said. She suggested a certificate of deposit instead. They were paying rates of up to 6 percent, depending on how much money you put in it and for how long.

Lee said the allure of passbook accounts is a holdover from the Great Depression. "They used to pay higher interest on passbook accounts because they didn't have to post it more than once a month," she said. "Today there's no advantage."

And there are a number of disadvantages, depending on where you bank. I called half a dozen banks and found out

Lack of easy access to your money could be a plus if you're trying to save, right? That's only true if you're a hard-core spender. For most of us, the high fees and low interest rates swing the balance. If you have a passbook account, you can do better elsewhere.

If it's discipline you're after, try a bank CD. Locking up the money makes it even less accessible - and you earn a better rate. If you've just been too lazy to move, get going. Try a money market account or even a statement savings account. Both offer guaranteed returns better than passbook accounts, which have returns typically equal to or less than the nation's inflation rate.

Passbooks aren't cool unless you're a kid.