This Disorder (attention deficit hyperactivity disorder) is a neurodevelopmental disorder defined by impairing levels of inattention, disorganization, and/or hyperactivity impulsivity. Inattention and disorganization entail inability to stay on task, seeming not to listen, and losing materials, at levels that are inconsistent with age or developmental level. Hyperactivity-impulsivity entails overactivity, fidgeting, inability to stay seated, intruding into other people's activities, and inability to wait symptoms that are excessive for age or developmental level.Attention-Deficit Hyperactivity Disorder is the most commonly diagnosed psychiatric disorder, occurring in 5-7% of children world wide.This study aimed to evaluate the association between LPHN3 gene and attention deficit hyperactivity disorder . Methods: The subjects were 2 groups; Group (I): included 30 patients with attention deficit hyperactivity disorder . And Group (II): included 30 apparently healthy individuals as a control group. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to determine the genetic association of attention deficit hyperactivity disorder  with the LPHN3 gene polymorphis (rs2349039). Results: The attention deficit hyperactivity disorder  group included 20 male (66.7%) and 10 females (33.3%), the mean age was 9.8±1.8 years. there was a statistically significant difference in the distribution of genotypes of the LPHN3 rs2349039 polymorphism in the attention deficit hyperactivity disorder  and control groups, (p=0.01). In attention deficit hyperactivity disorder  group; individuals with CG genotype were 5.8 folds to have attention deficit hyperactivity disorder  than CC individuals. Also, those with GG genotype were about Six times more likely to have attention deficit hyperactivity disorder  than CC ones.