About five years ago, Maria Coco became suspicious about a $200,000 investment that her 80-year-old mother had made with a broker who then failed to send her any account statements. Coco grew especially alarmed once she tried to withdraw some of her mother's money, and the broker's check bounced.

Her mother had apparently fallen prey to a scam — commonly known as a Ponzi scheme — whereby a financial adviser illegally uses new investors' money to pay existing investors, according to Massachusetts securities regulators.

Coco was fortunate: She was eventually able to recover about half the money this year with help from her lawyer and the Massachusetts securities department.

But the recovery was bittersweet. It was too late to use the money for what it was intended: to care for her mother at home.

Two years ago, Coco was forced to put her mother in a nursing home, where she died in early 2006, because there wasn't enough money to hire a caretaker for her at home.

"This was one of the worse experiences in my entire life," says Coco, 52, who lived with her mother for the last 15 years of her life. "I've had breast cancer twice, lost a child, and this was right up there. I was powerless."

Each year, slick-talking scammers call your parents, come into their homes and invite them to seminars. They peddle promises of risk-free investments and gargantuan sweepstakes winnings. Then they take your parents' money and disappear.

The Federal Trade Commission estimates that 1.7 million seniors 65 and older (or 3.4 million people 55 and older) were fraud victims between mid-2002 and mid-2003, the latest period for which figures are available. It's a problem that experts say will balloon as 79 million baby boomers age. Already, nearly a third of investor complaints to state regulators come from seniors 50 and older, according to the North American Securities Administrators Association.

"It's going to be a learning experience for the boomers to make sure that (fraud) doesn't happen to them as well as their parents," says Sally Hurme, a project manager with AARP.

Among the top traps ensnaring investors this year, according to the securities administrators association: oil and gas investments, Internet fraud and speculative investment products pitched at free-lunch seminars.

Investors of all ages can be fleeced. But the elderly tend to be more vulnerable because they've accumulated a lifetime's worth of assets and have free time to listen to sales pitches. "They may not get enough attention from their family and crave the attention," says Joseph Borg, president of the NASAA.

When seniors are scammed, their adult children often bear the burden of trying to recover the money — and of supporting parents who may have just lost a big chunk of their savings.

Sonia Tanner, 50, of Novato, Calif., has dipped into her own nest egg — and will likely have to delay retirement — to help pay for a 24-hour caretaker for her mother, Betty Tanner, who lost more than $300,000 to scammers. The fraudsters told her she had won millions of dollars but needed to pay taxes and other fees to claim the money.

"They said, 'Don't tell your children,' " Sonia says. " 'They're going to be so thrilled when you've won.' "

The con artists gained her mother's trust by calling her multiple times a day for months. By the time Sonia intervened, she says, her mother, now 77, felt so emotionally intimate with the scammers that she would hang up the phone saying "I love you" to them.

Before her mother developed Parkinson's disease in recent years, she was "lucid and swift," Sonia says. That's why it didn't occur to her to monitor her mother's finances.

The belief that investors who are financially knowledgeable won't fall prey to fraud can make elderly parents — and their adult children — less vigilant. But seniors who are fraud victims tend to be more financially literate than non-victims, according to a 2005-2006 study by Wise Senior Services, an advocacy group for seniors, funded by the NASD Investor Education Foundation. "They know just enough so they think they can control the situation," says Grace Cheng, CEO of Wise Senior Services.