Portuguese striker Helder Postiga has moved from Porto to Sporting Lisbon in a three-year deal worth 2.5 million euros.
Sporting's Diogo Filipe Viana will go in the other direction as part of the deal, where he will join up with the Portuguese champion's reserves team.
The deal, confirmed on Sunday, brings on an end Postiga's long association with Porto, whom he played for firstly from 1999 to 2003.
He then briefly moved to Spurs in 2004 but returned back to Porto in the same season, before being loaned out to French first division side St Etienne the following term.
He was then sent to Greek first division side Panathinaikos at the beginning of this year.
The 25-year-old is part of Luiz Felipe Scolari's Euro 2008 squad and has been selected 32 times for the national side since 2003, scoring 10 goals.