Abstract: Twenty two cases diagnosed as Attention Deficit Hyperactivity Disorder (ADHD), aged 6-10 years, chosen to study the correlation between developmental, behavioral and genetic factors in relation to some biochemical parameters. Another group of 22 healthy normal children of the same matched age and sexes were collected as control group. All cases and control children were subjected to full clinical and neurological history and examination, anthropometric measurements and behavioral assessment. Levels of folic acid, vitamin B12 and T3, T4 were estimated, for both cases and controls. Cytogenetic examination of peripheral blood lymphocytes were done for cases only. Chromosomal abnormalities were detected in 6 cases out of 22 cases. There was a significant decrease in the weight and BMI, as compared with controls, these decrease was highly significant among those with chromosomal abnormalities. Regarding the behavioral assessment, a significant decrease in three of the four components of Vineland Adaptive behavior scale: (communication, daily living skills and socialization), as compared with controls, this decrease in the three components was highly significant among those with chromosomal abnormalities. A non significant increase in the score of the motor skills, as compared with controls, while significant increase in it`s score was found among those with chromosomal abnormalities. Biochemical studies showed no significant decrease in T3 and T4 levels as compared with controls, while levels of Folic acid and Vitamin B12 showed significant decrease as compared with controls, this decrease in their levels showed highly significant decrease among those with chromosomal abnormalities. We concluded that this study is the first study in our knowledge examining the correlation between developmental, behavioral and genetic factors among children with ADHD in the same subject group. ADHD is multifactorial and is associated with a remarkable increase in chromosomal abnormalities, which affect behavior and anthropometric measurements.