Why Millionaire Investors Are Holding On to Cash

Adam Jeffery | CNBC

Today's wealthy investors seem to have split personalities.

Part of them is brimming with confidence and optimism. Survey after survey shows that they are back to pre-crisis boom years when it comes to their outlook for their own finances, their investments and their retirements.

Then there is the darker side. When it comes to their outlook on the broader economy or in stock markets, they take a dimmer view.

This contrast was on view in a recent survey from U.S. Trust. Its "Insights on Wealth and Worth" survey—which polls people worth $3 million or more (one-third of respondents had $10 million or more)—showed that 88 percent of respondents feel financially secure today and 70 percent feel confident about their financial security in the future.

A majority of millionaires now place a higher priority on growth than wealth preservation—a marked reversal from last year, when preservation topped growth.

(Read More: Top 10 Cities With the Most Millionaires)

However—and this is where the dual personality comes in—the wealthy are still holding mountains of cash. The survey found that 56 percent have a "substantial" amount of cash. Only 16 percent of them plan to invest that cash in the next couple of months. And only 40 percent plan to invest it over the next two years.

This may be a sign that the wealthy are confident psychologically, but they're not quite ready to give up the security of their cash holdings, said Keith T. Banks, president of U.S. Trust and Bank of America Private Wealth Management.

(Read More: Tax Collections From Wealthy Are Saving Government)

"It may be a case where the psychology comes first," he said. "They just haven't taken that next step with their money yet."

How much cash do the wealthy hold? There is no hard data. But a study from the Harrison Group and American Express Publishing last year found that the American affluent—those with at least $100,000 in disposable income—had at least $6 trillion in savings. Harrison said that number could balloon to $12 trillion by 2014.

Unless, of course, the wealthy start putting that money into the market.

—By CNBC's Robert Frank. Follow him on Twitter @robtfrank.