With the sixth pick in the first round of the 1969 NBA draft, the San Diego Rockets selected Smith. A year later, he was drafted by the Cleveland Cavaliers in the 1970 Expansion Draft. In his first game with the team, he scored 21 points. He helped contribute to the Cavaliers winning the NBA Central Division title in 1976, and was part of the Miracle at Richfield, winning Game 2 of the Semifinals vs the Washington Bullets.
In 11 seasons, Smith played in 865 games and logged 22,407 minutes. Smith was especially noted for his ability to hit jump shots from long range. His outside jump shots often were taken from today's 3 point range. For his career, he recorded a .449 field goal percentage (4,776 FGs made out of 10,642 attempts). Smith also had a .798 free throw rate (1,307-of-1,637) and also accounted for 3,630 total rebounds, 1,734 assists and 10,882 points. Smith was known for his rainbow jumper, now utilized by other forwards such as Dirk Nowitzki.
His best season was in 1974, when he scored 15.9 points per game and had a .483 field goal percentage.
Smith played the full 82 games in four of his seasons, but he also led the league in turnover percentage in his final three seasons. He scored his 10,000th point in the middle of the 1979 season.
On October 27, 1979, he was traded for a 3rd round draft pick (used to pick Stuart House) to the San Diego Clippers. Oddly enough, the Cavaliers retired his number over a month later, while he was still playing with the Clippers. Fittingly, he ended his career in the same place it had started. After one season (the first year that the three point line was instituted), he was drafted by the Dallas Mavericks in 1980 Expansion Draft, but he never played for them, retiring at the age of 34.