In the same period, he was one of the most outstanding players of the Italian U21 team which reached the semi-finals in the 2002 UEFA European Under-21 Football Championship.

Following his exploits in the semi-final, fellow Middlesbrough striker Jimmy Floyd Hasselbaink declared "Massimo, I love him until I die... it's unbelievable".

[11] Despite these heroics, he made few appearances for Middlesbrough in the following season and in January 2007, Maccarone moved to Siena in a free transfer, signing a three-year contract.

[15] He finished the season with six goals, and added 13 in the following (club best by a long margin), as Siena achieved two consecutive 13th league places.

[32] He made his senior international debut on 27 March, in a friendly match against England in Leeds; he came on as a late substitute, with the score level at 1–1.

In injury time, Maccarone was fouled in the area by the English goalkeeper David James, allowing Vincenzo Montella to score the winning goal from the penalty spot.

[35] He made his second and final appearance for the Italian senior side on 16 October 2002, in a 2–1 away defeat against Wales in a European Championship qualifying match.

[36][37] Following his retirement, he stayed on at Carrarese as a technical collaborator under his former boss Silvio Baldini for the 2020–21 season, leaving in April 2021 following the appointment of Antonio Di Natale as the club's new head coach.

[38] In June 2022, Maccarone took on his first role as head coach, accepting a job offer from Tuscan Serie D amateurs Ghiviborgo.