Diefendorf Hall houses several large lecture halls as well as other centrally scheduled classrooms. It houses the Attention Deficit Hyperactivity Disorder Program administered through the Psychology Department.

Charles Haas Diefendorf (1891-1975) was a banker who was very active in civic, cultural, and philanthropic affairs in Buffalo. He was a member of the University Council for about 20 years.He was awarded the Chancellor's Medal in 1961.