Lack takes over from Bob Wright who will devote more time to his role as vice-chairman and executive officer of NBC parent, General Electric. Wright will also become chairman of NBC.
Lack, currently NBC's news chief, will report directly to Wright who has been NBC's CEO and president since 1986. Wright will retain control of NBC Sports, its Olympic coverage, CNBC International and NBC's staff operations.
Lack will oversee NBC's news and entertainment divisions, the cable networks CNBC and MSNBC, and the sales team.