 Maroussi reached the final of the third-tier level FIBA Europe League's (later called FIBA EuroChallenge) 2003–04 season, but they lost in the final to the Russian club UNICS Kazan.In the Greek Cup, Maroussi reached the Greek Cup Final Four in the 1999–00 season and the Greek Cup Final in the 2001–02 season.Under the club's head coach at the time, Panagiotis Giannakis, and with the young star play-maker of the club at the time, Vassilis Spanoulis (recipient of the Greek League Best Young Player and Greek League Most Improved Player awards in 2003 and 2004), the club finished in second place in the Greek Basket League 2003–04 regular season, with a 21–5 record.