The Conference Board's measure of CEO confidence fell to 38 in the first quarter of this year, its weakest reading since the fourth quarter of 2000 when it was at 31.

"CEOs' assessment of current conditions suggests we're still mired in a period of extremely slow growth, and while their short-term outlook moderately improved, they remain quite cautious," said Lynn Franco, director of The Conference Board Consumer Research Center.

Only 3% of CEOs said economic conditions had improved in the first quarter, compared with 7% in the fourth quarter, according to the index.