Bologna's Champions' League hopes took a massive blow with this shock home defeat
It was the relegation strugglers who broke the deadlock with a spectacular chip from defender Tosto.
Piacenza dominated the first 30 minutes in an exciting encounter with good chances for Vincenzo Sommese and Carmine Gautieri, but as they began to tire the Rossoblu came out of their shell. Renato Olive and Julio Cruz failed to turn in from close range.
Alessandro Cardone was forced off just before the break after sustaining a blow to the head.
Beppe Signori came on for the second half, but it was Piacenza who doubled their lead. A defensive error from Giulio Falcone allowed Eusebio Di Francesco to spring the offside trap and turn a low drive past the helpless Pagliuca.
Signori would have re-opened the game had it not been for Sergio Volpi's crucial goalline clearance. The goal came soon after as Fabio Pecchia's header came off the bar, but into the path of Salvatore Fresi. It was not enough to overturn a strong Piacenza performance.