A BSTRACTBackground: ADHD is a neuro-behavioral disorder that is typically manifested during childhood and often persists into adulthood, it is a complex disorder influenced by many genes, genetic and environmental risk factors co-occurring in a non-random fashion. The MTHFR gene C677T polymorphism affects both nucleotide synthesis and DNA methylation, and is associated with reduced folate bioavailability and folate metabolites. Objectives: To assess the relationship between Methylenetetrahydrofolate Reductase (MTHFR) gene polymorphisms (C667T) allele and Attention Deficit Hyperactivity Disorder (ADHD) in a sample of Egyptian children. Methodology: Out of 402 reviewed patients regularly attending the Psychiatric clinic, According to criteria of inclusion and exclusion a sample of 30 ADHD children were enrolled in this study. The patients were selected by simple random sample during the period from January to August, 2015 with age ranged from 6-to 12-year old. A matching number of 30 healthy children with normal developmental and psychiatric evaluation, of compareble age and sex, were randomly recruited as a study control. MTHFR gene polymorphism (C677T) allele was investigated in the selected sample.