 On 28 June 2003, Maccarinelli, known as "the Big Mac" won the vacant WBU cruiserweight title when he defeated Bruce Scott by fourth-round TKO.He made seven successful defences of his WBU title before vacating.On 8 July 2006, Maccarinelli fought against former World Boxing Council (WBC) cruiserweight champion Marcelo Fabian Domínguez for the WBO interim cruiserweight title.