Do CFOs who serve on the boards of other companies bring back valuable insights that help their own companies deliver greater value to shareholders? Or are the CFOs of outperforming companies simply more attractive board candidates?

Either way, the outperformance is plain to see. Among the 482 publicly held companies in the S&P 500, 102 of their finance chiefs served on at least one outside board in 2012. Among them, 63 have been in the CFO seat at their current company for at least three years. The median three-year total shareholder return (TSR) delivered by those CFOs’ companies from 2010 to 2012 was 19.9 percent, compared to 15.2 percent for companies whose CFOs didn’t serve on a board, according to an analysis of SEC filings by executive-compensation data firm Equilar.

Historically, the methodology for building a board of directors was often characterized as tapping an “old boy’s network,” in which board composition typically was fairly homogeneous, without great diversity, accountability or independence, Equilar wrote in its report. But because of the high-profile instances of corporate malfeasance in the 2000s, significant legislative and regulatory actions that are holding boards to higher performance standards and the ever-expanding global marketplace, today’s boards seek a deeper pool of talent from which to recruit.

Specifically, more boards are bringing on CEOs of other companies – 234 of the ones within the study group served on outside boards in 2012 – as well as CFOs.

But the TSR performance for the 27 companies where both the CEO and CFO served on at least one outside board, 19.5 percent, was actually slightly less than those where only the finance chief did so.

Equilar noted that service on outside boards is becoming part of some companies’ succession-planning process. CFOs that perform such service have a leg up as potential candidates when the CEO slot opens up.

“Serving on an outside board provides the opportunity for executives to gain exposure to complementary industry strategies and challenges, learn from experienced board colleagues, and further refine leadership abilities,” the research firm wrote. And taking advantage of those opportunities behooves not only CFOs’ career outlook but also the companies they work for.

Still, there is a question as to whether the above-mentioned TSR premium is more a result of a CFO serving on an outside board, or a cause of such service. “We’d have to do much more detailed research to establish that, but it is a chicken-and-egg issue,” Aaron Boyd, Equilar’s director of governance research, tells CFO. “It makes sense that the CFO of a company that is getting attention for performing well is more likely to be invited to join a board, but they also can gain new perspective that they can use to continue growing TSR at their own company. I don’t think you can say it’s definitively one or the other.”

At any rate, companies whose CFOs serve on outside boards are larger than others, and those finance chiefs make more money than their non-outside-director counterparts. The median market capitalization for those two groups was $14.9 billion and $10.6 billion, respectively, and median total 2012 compensation was $3.4 million and $3.1 million, respectively.

Meanwhile, the study found that women CFOs are far more likely to get board seats than men. Among the 102 finance chiefs who were on outside boards, 20 were women. Those 20 represented 60 percent of the women CFOs among the study group’s 484 companies. The 82 men who served on boards represented just 22 percent of male CFOs in the study group.

Many boards have, in fact, sought to diversify their membership by adding women directors in recent years.