Attention deficit hyperactivity disorder (ADHD) is considered the most common child psychiatric disorder in the United States of America. Despite the high prevalence (estimated at 3-5%), little is known about the level and source of knowledge about ADHD among those affected by the disease, and about cultural and ethnic variations in knowledge levels and information sources. This represents a serious deficit, because health behavior, including demand for health services, is thought to be strongly influenced by knowledge or beliefs held by individuals and their networks. Furthermore, recent research suggested minority children may be less likely to receive services for ADHD. To examine possible differences in ADHD knowledge and information source, a sample of 486 African-American and white parents of children at high risk for ADHD were surveyed by telephone and subsequently participated in face-to-face interviews addressing their explanatory models of ADHD. Results revealed significant ethnic differences in knowledge and sources of information about ADHD. Fewer African-American parents than white parents indicated that they had ever heard of ADHD (69% compared to 95%, P<0.001), or that they knew some or a lot about it (36% compared to 70%, P<0.001) African-American parents were more likely to attribute ADHD to excessive sugar in the diet than whites (59% compared to 30.0%, P<0.001). Finally, even though the physician was listed as the most preferred information source for both groups, only 17.5% of African-American parents reported they had received information about ADHD from the physician compared to 29% of whites (P<0.01). African American parents reported less use of and less preference for written informational materials (newspapers, journals, library) than white parents. We conclude that substantially more research should be undertaken to examine the relationship between ethnicity and ADHD knowledge, to inform culturally appropriate education campaigns and to improve access to services for this important treatable child mental health condition.