The appointment of Vanessa Wittman as finance chief at Dropbox is the latest high-profile example of how the type of CFO a company needs shifts with its circumstances.

Wittman’s hiring was interesting given that when Dropbox’s smaller competitor, Box, went public in January, CFO and co-founder Dylan Smith remained at the finance helm. As often as not, a startup preparing to go public does what Dropbox did: bring in someone with public-company experience.

David Axson

Counter-intuitively, however, that person doesn’t necessarily have prior experience as a company’s finance leader. In many cases, he or she comes from a divisional CFO role, and just as often from an operational leadership role, such as president of a division, notes David Axson, managing director for CFO and enterprise value at Accenture Strategy.

“You have to look at the individual,” Axson says. “You want the person who can communicate credibly to potential investors, especially during your pre-IPO road show, and to the analyst community. That’s Job 1.”

Strong divisional leaders may be the best option for smallish startups planning to go public, which are unlikely to lure a lead CFO away from a large, established company. In the case of divisional CFOs, many are blocked from moving up to the top corporate finance seat and see moving to a smaller company as a chance to achieve that.

Such people “are tightly connected to the quarterly earnings cycle, work with the corporate CFO on the preparation of materials, are often present at earnings calls, [speak] at analyst conferences, and are familiar with the regulatory environment,” says Axson.

Indeed, an incoming CFO may have far more business experience than the CEO he or she will be reporting to, especially in the case of technology startups. “At companies that were started by young entrepreneurs, often the CFO is seen as the adult supervision in the room,” Axson notes.

Wittman herself comes to Dropbox from a divisional CFO role, but she’s hardly one of the small fry looking for her first big break. Dropbox, with its $10 billion valuation and 300 million users worldwide, was able to land a finance chief with a stellar pedigree.

Wittman was CFO at Marsh & McLennan, currently a $12 billion company, from 2008 to 2012, when she joined Google to run finance at Motorola Mobility, a $12.5 billion unit it had acquired the previous year. Earlier in her career, from 2003 to 2008, she helped clean up the financial mess at cable-television giant Adelphia, which had been undone by an accounting scandal.

She’s referred to that exercise, which in part involved selling off the company in pieces, as “extreme finance.”

At Dropbox she replaces Sujay Jaswa, who had raised more than $1 billion in financing during less than a year at the company. Jaswa was the CFO Drobox needed last year, and Wittman is the one it needs this year.

“It’s a different skill set, taking a company through an IPO and being a public-company CFO, compared with someone has who is good at shepherding a company through its early rounds of financing and being [an internal] jack of all trades,” Axson says.

“To create a finance organization that’s scalable as a public company, the CFO must be outward-looking, the CEO’s right-hand person in the dialogues with the Street and the board.” Such a skill set is in demand not only for IPOs, but also for large public companies that break themselves up by spinning off multiple public entities, Axson observes.

If communicating with the investment community is Job 1 for a CFO coming to a company preparing to go public, then Job 2 is managing the increased compliance and reporting requirements. Research released by Accenture last September underscores both points.

First, in a survey of 617 finance executives, regulatory issues were identified as having the biggest impact on finance-function performance, with 39% of participants reporting a “high” impact and 56% a “moderate” impact. “Whether it’s Basel III if you’re a bank, Sarbanes-Oxley still, international financial reporting standards, emerging Dodd-Frank regulations, you name it, the scrutiny that falls upon a public company is one of the biggest variables a CFO has to deal with,” Axson notes.

Second, participants were presented with a list of 14 challenges for finance executives and asked to identify their greatest challenges (selecting “all that apply”). Coming in third, at 48%, was “managing the complex needs of stakeholders.” Of course, going public brings in a major new category of stakeholders: public shareholders.