CBS Corp. has promoted Joseph Ianniello to exec veep and chief financial officer. He succeeds Fred Reynolds, the Eye’s longtime financial chief who is set to retire in August.

Ianniello takes the financial reins of CBS at a volatile time for media congloms in general and CBS in particular. The Eye’s stock has been on a roller-coaster ride this year along with the market gyrations. CBS’ credit rating was downgraded earlier this month by Standard & Poor’s on concerns about CBS’ heavy reliance on advertising sales in the recessionary environment.

CBS and other media stocks have taken a hit in recent weeks as fears rise on Wall Street that the volume and pricing on this year’s upfront advertising sales will be down sharply from the roughly $9.2 billion taken in last year by the Big Four nets and CW. On Monday, CBS shares closed down 6.8% to $6.84, though it was trending up in after-hours trading.

Despite these downbeat indicators, CBS recently had no trouble refinancing $1 billion worth of debt that was to come due next year. The Eye found plenty of takers for five- and 10-year notes at an interest rate that would likely have been much higher just a few months ago, Ianniello said.

The response to the senior note offering is a sign that credit markets are finally recovering and a strong indication that “investors are starting to feel the bottom,” Ianniello said. “And as the recovery comes, we’re going to be the biggest beneficiary” among the Big Four networks given CBS’ solid ratings performance last season.

“Investing in premium content is what is driving this company forward,” Ianniello added. “My job is to make sure there’s enough gas in the tank to get us to where (CEO) Leslie (Moonves) wants to go.”

CBS has enough cash on hand to pay down its next big debt bill of $415 million, coming due in July 2010, Ianniello said.

Ianniello has been with CBS since 1997, rising through a series of finance posts. He served as a veep of business development and senior veep and treasurer of Viacom following the Eye’s merger with Viacom. When those two companies split up again in 2006, Ianniello served as senior veep and treasurer of CBS and was upped to deputy CFO under Reynolds in November.

In announcing Reynolds’ retirement, Moonves hailed the exec for his “steady hand and keen business instincts.” He noted that Reynolds had guided the Eye through a string of complex mergers and acquisitions since the mid-1990s, including the 2000 merger with Viacom and its spinoff six years later.

Reynolds will step down as CFO next month and continue as exec veep and an adviser to CBS through mid-August. Reynolds joined CBS through Westinghouse Electric Corp.’s 1995 acquisition of the Eye. Reynolds also served as prexy of the CBS Television Stations group from 2001 through 2005.

Before he came to Westinghouse in 1994, Reynolds spent 13 years in various finance posts at PepsiCo.