Smith scored a 16 out of 50 on the NFL-administered Wonderlic test when he first took the exam in 1998. His agent Leigh Steinberg hired a tutor to help improve his score for the 1999 scouting combine, and he scored a 37 on the second try.
Prior to the draft, there was an effort by New Orleans Saints' head coachMike Ditka and management to get the Cincinnati Bengals' high draft position so the Saints could get Ricky Williams. The final offer, which was refused by Bengals management, was for nine draft picks, several extra in that year as well as many the next year. Instead of taking the trade, the Bengals stayed with their initial decision to draft Smith, who, while athletic, (he had also played two years of minor-league baseball and ran a 4.66 40-yard dash) was still largely unproven, having only succeeded at the college level for one season.
Smith missed a large portion of training camp during his rookie season in 1999 due to contract disputes. On August 24, 1999, he signed a seven-year contract worth up to $56 million with a $10.8 million signing bonus.
Despite showing athleticism in his early games, he failed to grasp the Bengals playbook fully, and never established himself with the team. His offensive coordinator from 2001–2002, Bob Bratkowski, said Smith "wasn't as diligent as he should have been" regarding his film and playbook study habits. During the four years he was with the Bengals, he started in only 17 games and threw just five touchdown passes next to 13 interceptions, eventually leading to his release on May 31, 2003, after riding the bench mostly during the previous two years.
In his first regular season action, replacing Burris in the second quarter on July 12, Smith struggled against the Toronto Argonauts. He finished 6-of-10 for 63 yards, no touchdowns and three interceptions. He also lost one fumble. He was then pulled at the end of the half. After an unimpressive showing against the Roughriders on October 8, 2007, going 4-of-12, for 37 yards, along with the impending return of a healthy Burris, the Stampeders released Smith on October 10, 2007.
In March 2010, Smith joined the University of California's football staff as a graduate assistant to work with the offense. Cal head coach Jeff Tedford previously coached Smith at Oregon when he was offensive coordinator.