Selected 24th overall by the Lakers in the 2003 NBA draft, Cook played primarily as a reserve during his four seasons with the team (2003-07). The 6-foot-9 forward out of Illinois was used sparingly in his first two professional seasons, playing primarily in support of Shaquille O’Neal and Caron Butler. After seeing more time on the perimeter under Coach Rudy Tomjanovich, Cook developed into the team’s top three-point shooter.
Coach Phil Jackson, upon his return to the team in 2005, began to play Cook more on the outside, and the former Big Ten Conference MVP responded by leading the team in three-point shooting percentage in addition to posting career highs in points per game, field-goal percentage and rebounds per game.
However, Cook struggled while battling injuries during the early part of the 2006-07 season and eventually lost his sixth-man role to Luke Walton. After appearing in six games the following season, Cook and teammate Maurice Evans were traded to the Orlando Magic in exchange for Los Angeles native Trevor Ariza. Cook signed a two-year deal with the Clippers during the 2010 off-season.