Career
Leyton Orient
Demetriou came through the youth ranks at English club Leyton Orient and signed his first full professional contract with the team in July 2006. He made his league début in November 2006 when he came off the bench in a 0–0 draw with Yeovil Town. He went on to make 24 appearances in his first year, in both league and cup competitions, mostly as a substitute.
The 2007-2008 season was a break through season winning the young talent award for Leyton Orient.
Demetriou himself has given much cr to ex-manager Martin Ling for giving him the chance to prove himself at this level of football particularly in the 2007-2008 season. Despite Leyton Orient struggling throughout the 2008-2009 season, Demetriou"s performances impressed the fans and he was linked with big money moves away to Premiership and Championship clubs Plymouth Argyle and Charlton Athletic.
AEK Larnaca
Demetriou officially signed for AEK Larnaca on 2 June 2010, for an undisclosed fee, to be able to progress as an international for Cyprus. He said he was very sad to leave Leyton Orient but had to move in order to play international football.
Anorthosis Famagusta
On 28 June 2013, Demetriou signed a 2+1 year contract with Anorthosis Famagusta F.C.
Walsall
On 1 July 2015, it was confirmed that Demetriou has signed a contract for Walsall for an undisclosed fee, pending International Clearance.
On 20 January 2009 he was called up to Cyprus squad for the first time by manager Angelos Anastasiadis. He made his début against Serbia in the 2–0 home defeat coming on as a sub for Demetris Christofi on 10 February. He was awarded man of the match award for his performance in this match.
