Last year, women held about 10 percent of the chief information officer positions at Fortune 500 companies. Yet of the top 10 highest-paid CIOs in 2010, women made up half the list, compared with only two the year before, according to data compiled by consulting firm Janco Associates.

The list shows that the top 10 CIOs made from $2.5 million to $5.11 million in total compensation, which includes salary, bonus, stock, options, pension, and perks. In 2009, the figures ran from $1.4 million to $8 million. Only four CIOs appeared on the list both years. While the average salary among the top 10 stayed steady at $537,100, the value of stock and options fluctuated. The overall average salary for CIOs was $175,363 as of June this year.

At the top of the list is Margaret M. McCarthy of Aetna (AET), who made $5.11 million in total compensation. That included $588,506 in salary, $837,312 in bonus, and $3.6 million in stock. The list is based on public data and does not include CIOs at companies that aren’t required to disclose salary information.

“Some of the biggest, most-well-known companies have female CIOs,” says Sharon Gillenwater, founder and principal of Boardroom Insiders, which maintains a database of Fortune 500 executive profiles.

McCarthy’s compensation was a fraction of went to the top-paid CIO in 2008. That year, Randall Mott, executive vice-president and CIO at Hewlett-Packard (HPQ) received $28.3 million in total compensation, including $690,000 in salary, $7 million in bonus, $2 million in stock, $1.5 million in options, and $16.1 million in a non-equity incentive payment. Subsequent compensation for Mott—who left several months ago during a management restructuring by former Chief Executive Officer Leo Apotheker—is not in the public record.

More CIOs Report Directly to CEO

A CIO’s compensation is highly dependent on the reporting structure within companies. “The reason you have CIOs being paid so much is because they’re reporting directly to CEOs,” says Victor Janulaitis, CEO of Janco.

In the U.S., about 28 percent of CIOs surveyed by Harvey Nash (HVN) and PA Consulting Group report directly to the CEO, up from about 21 percent in 2010 and 15 percent in 2009, which indicates growing influence. CIOs typically report to chief financial officers in companies where the role is seen as less strategic and more about efficiency and utility, says Hsiu Mei Wong, managing consultant with PA Consulting Group’s IT Practice.

Here are some of the top paid CIOs of 2010, according to Janco. The list is based on corporate filings with the U.S. Securities & Exchange Commission. Salary information for CIOs is only made public when it ranks among a company’s top-paid executives.

1. Margaret M. McCarthy, Aetna
Senior vice-president of innovation/CIO, from January to November 2010
(She’s currently executive vice-president of operations and technology)
$5.11 million

2. Lori A. Beer, Wellpoint (WLP)
Executive vice-president/CIO, from May 2008 to October 2010
(She’s currently executive vice-president of enterprise business)
$4.47 million

3. Glen Salow, Ameriprise Financial (AMP)
Executive vice-president of service delivery and technology
$4.15 million

4. Robert Carter, FedEx (FDX)
Executive vice-president/CIO, January 2007 to present
$3.21 million

5. Deborah Butler, Norfolk Southern (NSC)
Executive vice-president of planning/CIO, June 2007 to present
$3.16 million

6. Matthew A. Carey, Home Depot (HD)
Executive vice-president/CIO, September 2008 to present
$2.86 million

7. Anna M. Ewing, Nasdaq OMX Group (NDAQ)
Executive vice-president of technology and market technology/CIO, February 2008 to present
$2.77 million

8. Gregory Framke, ETrade (ETFC)
Executive vice-president and chief operating officer/CIO, 2005 to present
$2.76 million

9. Lisa Bachmann, Big Lots (BIG)
Executive vice-president of supply-chain management/CIO, March 2010 to present
$2.61 million

10. David A. Barnes, UPS (UPS)
Senior vice-president/CIO, 2005 to present
$2.53 million