Los Angeles County district attorney's spokeswoman Jane Robison says Redmond O'Neal's graduation from the treatment program has led to the dismissal of two drug-related cases.
Robison says O'Neal will remain on probation for another two years for a case in which the 25-year-old brought drugs to a jail facility.
O'Neal's completion of the diversion program was announced during a court hearing Thursday in Los Angeles.
Among the charges dismissed was a case filed after sheriff's deputies found drugs at Ryan O'Neal's home in 2008 while his son was on probation.
Redmond O'Neal's attorney, Richard Pintal, did not immediately return a call seeking comment.