Tomaszewski was born in Gostynin, Poland, in 1974. He received his first guitar lesson at a cultural centre in Płock, when he was ten years old. Beginning in 1990, Tomaszewski attended Warsaw's Fryderyk Chopin Music Academy, studying under Ryszard Bałauszko. He later completed his studies under Bałauszko at the Białystok branch of the Academy. As a postgraduate, Tomaszewski studied in 1998 and 1999 at both the Conservatorio de Musica in Las Palmas, in Spain, under Carlos Oramas, and with Alberto Ponce at the École Normale de Musique de Paris.