The "Hunger Games" actor did not like her partying habits. The couple has been dating since 2009, but separated twice in 2010.
"Miley and Liam are done. It is over. She likes to party really hard and can be pretty wild. It became a problem for him," contactmusic.com quoted a source as saying.
Another source said: "They have broken up before, and are broken up again now. There was drama because she suspected he had a wandering eye. And she recently tweeted a denial that he cheated.
"While Miley has insisted they are still together, right now they are very, very much apart."
However, despite the split, friends close to Cyrus are hopeful they will reconcile their differences and reunite once again.
"Miley is a fiery character, and they do fight, but she is crazy about Liam. She isn't ready to accept it might be over for good," said a friend.