The following season, Smith joined Championship club Queens Park Rangers, becoming a regular in a team challenging for promotion to the Premier League.

His father Dave, a chartered surveyor and former Watford youth team player, helped coach with the academy during his son's time there.

[6] In 2014, he and his brother Jack took over the sales arm of an estate agent and chartered surveyors with its headquarters in Bushey Heath, near Watford.

[2] After only playing for Comets Sports club in Sunday league football for two years, he was given a chance by his father at Watford in a county trial at the age of 14 and signed with them again.

[2] Manager Graham Taylor gave Smith his debut for Watford on 18 November 1997, bringing him on as a substitute in a 2–1 Second Division win over Oldham Athletic.

[7] Smith did not play another league game in 1997–98, but made eight appearances for Watford as they qualified for the play-offs in the 1998–99 season, where the club gained promotion to the Premiership.

He established himself in the team during the club's first Premier League season, making 23 appearances and scoring two goals, including one at Vicarage Road against Manchester United.

[8] Although Watford were relegated in 1999–2000, Smith remained at the club, playing under Gianluca Vialli and Ray Lewington, and scoring on his sole appearance for the England under-21 team in a 6–1 win against Georgia under-21.

[10][11] However he was dropped to the bench for Watford's 2003 FA Cup semi-final with Southampton, with on-loan striker Michael Chopra chosen instead.

He then went on trial with West Ham United, but Glenn Roeder was sacked as manager, and his replacement Alan Pardew chose not to sign him permanently.

[2] Smith spent one season at Sunderland, helping them to finish third in the Championship, after which they lost 5–4 on penalties to Crystal Palace in the play-off semi-finals.

[13] For the second consecutive season Smith scored the winning goal in an FA Cup quarter final,[12] and this time he was selected to play in the semi-final, which Sunderland lost 1–0 to Millwall.

[14] Smith bought a house in the Sunderland area and anticipated discussing a two-year contract at the end of the 2003–04 season.

[17] Smith came second in the voting for Player of the year behind Iñigo Idiakez, but did win the inaugural Derbyshire Fair Play award.

"[2] He was close to signing for Sheffield United, before he was the subject of an approach from former club Watford, who had just won promotion to the Premier League.

One of his goals was the equaliser in a 1–1 draw against Blackpool on the last day of the regular season, which secured Watford's place in the 2007–08 Championship play-offs.

[31] On 27 August 2009, it was confirmed that Smith had signed a four-year deal with Premier League club Portsmouth for an undisclosed fee believed to be in the region of £1.8m.

[36] He suffered a broken nose following Daniel Sturridge elbowing him in the face in the following game, and subsequently missed the FA Cup semi-final.

[7][40] Smith provided the assist for Heiðar Helguson in a 2–1 win against Crystal Palace on 2 October and has since made many positive contributions to the QPR team but found starts hard to come by in the early days of his Rangers career.

[6] He is a quick player capable of kicking the ball with his weaker left foot,[50] and prefers being part of a team that plays passing football, than one that employs a more direct style.