The 64-year-old Rohr will step down at the annual shareholder's meeting April 23, but will remain executive chairman for a year while the bank transitions to Demchak's leadership.
The 50-year-old Demchak was hired by PNC as chief financial officer in 2002, when he left JPMorgan Chase. Since then, he's become PNC's senior vice chairman in 2009 and president last April.
Rohr was hired by PNC in 1972 and has headed the bank since May 2000. During that time, the bank's employees have more than doubled, to 56,000, and its assets have quadrupled, to $305.1 billion.