Objective: The current research focuses on neurotransmitter serotonin levels and the work was planned to study the comparison between children (female and male) as well as the special need children (with abnormal behaviors ADHD). Materials and methods: Total 86 children from certain primary school were selected, 56 of them were with ADHD (27 boys and 29 girls were present) and 30 healthy individuals (16 boy and 14 girls). ADHD was diagnosed by certain questionnaire form prepared for this study, blood samples were gathered, and were send for serotonin examination which was achieved with a certain enzyme linked immune sorbent assay (ELISA). Results were analyzed using special statistic program (SPSS version 18). Results: The collected data indicate that serotonin level was high (121.70 ± 4.05 ng/ml) in ADHD children compared with normal children (85.64 ± 2.43 ng/ml), and highly significant decrease in level of serotonin transporter in ADHD than in control samples (9.87 ± 0.29; 13.17 ± 0.50 ng/ml correspondingly). Conclusion: The increase and decrease in the level of serotonin serum and serotonin transporters could be related to the environmental issues that contribute to the disruption of behavior particularly rise in poor security and hot regions.