New Video: ET sits down for an exclusive one-on-one with "Dancing" star MARIO and his mother with our KEVIN FRAZIER.

Mario hopes to win DWTS to benefit his Do Right Foundation, which helps children affected by drug abuse in the home and in under-resourced communities.

The subject is very close to his heart -- he and his mother went public with her struggle with heroin on the critically acclaimed MTV News Docs Presents: "I Won't Love You to Death: The Story of Mario and his Mom."