According to self-report data, blacks use less alcohol and drugs than whites. Black students in my classes have argued that this is evidence that the criminal justice system is biased since blacks are arrested at high rates for drug-related offenses. (Let's leave aside the question of dealing, and that research suggests that blacks under-report deviant behavior).
Treatment data, however, reveal that blacks are more likely to abuse alcohol and drugs. In 2008, 21.3% of Americans admitted for treatment of a drug or alcohol problem were black, although they are only 13% of Americans (and are less able to afford treatment). Black admissions are particularly high for crack and marijuana, but blacks are overrepresented even among those admitted for alcohol (16.8 percent of the total).