For fiscal year 2011, federal agencies have requested $15.5 billion for drug control related functions (actual spending in FY2010 was $15 billion). To get a sense of how that request breaks down by agency, I made the following chart from data in the appendix of the 2011 National Drug Control Strategy report (pdf).
The above chart is not that informative because it mixes spending on treatment and prevention with that on domestic enforcement, interdiction, and international activities. Total FY2011 funding for treatment and prevention requested by the agencies is $5.6 billion (actual spending in FY2010 was $5.3 billion). Since I’m principally interested in treatment and prevention programs, I made a second chart from the same data source for just that component of spending, by agency.
It’s not surprising that HHS dominates the treatment and prevention budget. It oversees Medicare, Medicaid, and block grants to states for substance use treatment and prevention. Notice that the VA is the second largest federal source of funding, though still more than a factor of ten smaller than HHS-based funding.