كتب : Hatem Maher
Christian Manfredini's goal cancelled out Dejan Stankovic's opener in the first half.
Both sides played with 10-men just four minutes after the start when Paolo Di Canio and Nicolas Burdisso were sent off because of a fight with each other.
Serbian midfielder Stankovic broke the deadlock in the 26th minute after connecting with Giuseppe Favalli's cross into the back of the net.
Manfredini equalized for Lazio just two minutes later when he chipped the ball over Inter keeper Francesco Toldo.
Inter need just a draw in the return leg of the quarter final that will take place in Giuseppe Meazza Stadium on the second of February.