De Castro, who spent 25 years in the radio industry, will be tapped as president of AOL Interactive Services to help AOL retain its lead in the market and to shape its content and services agreements. De Castro, who will report to AOL's chief operating officer, J. Michael Kelly, will replace Jonathan Sacks, who announced his retirement in February to pursue personal interests.
The appointment comes two days after AOL Time Warner announced that Barry Schuler, CEO of the troubled AOL division, would his post. AOL Time Warner co-COO Bob Pittman will assume Schuler's role; Pittman retains his duties in overseeing the media giant's operations.
On Thursday, Pittman highlighted de Castro's previous experience as an asset to the online service.
De Castro "thrived in the highly competitive radio business because he understands audience segments and knows how to develop programming that appeals to everyone from teens to seniors," Pittman said in a statement.
The AOL division, once viewed as AOL Time Warner's growth engine, has seen its star fall over the past year. The most immediate concern is AOL's advertising business, which has watched its revenue declinefrom the previous year, excluding advertising purchased by other AOL Time Warner companies.