The former economy minister helped to finance the pro-Europe protests that led to pro-Kremlin president Viktor Yanukovych's ouster and escape to Russia last month.
Yanukovych's deputy Sergiy Tigipko was backed by just over 7% of respondents, while over 4% supported Mykhailo Dobkin, the ex-governor of the ethnic Russian-dominated eastern city of Kharkiv.
Poroshenko is estimated to have a $2-billion (1.4 billion-euro) fortune, making him one of the 10 richest men in Ukraine.
Like many oligarchs, he made his money on the ruins of the Soviet Union in the 1990s.
The towering 48-year-old started out selling cocoa beans, buying up several confectionery plants which he later united into Roshen.
He also owns a company that makes minibuses.
Copyright Agence France-Presse, 2014