Aim: The aim of our study was to investigate the relation between lead and mercury exposure and some chronic neurodevelopmental diseases in children. Material and Method: In the Departments of Pediatric Neurology and Pediatric Psychiatry clinics, children diagnosed with motor-mental retardation, epilepsy, attention deficit/hyperactivity disorder and autism were included in the study as the study group (39 boys and 20 girls). Age and sex matched healthy children were used as controls. Blood lead and mercury levels were measured using the atomic absorption spectrophotometry method. The possible effect of environmental factors that could cause exposure to heavy metals (such as vaccination, fish consumption and the number of dental fillings the mother had) were also considered. Results: The average age was 7.66 years and 7.68 years in the study and the control groups, respectively. The average lead level in the blood was 1.91 μg/dl in the study group, 2.19 μg/dl in the control group. The average mercury level in the blood was 0.84 μg/L in the study group and 0.99 μg/L in the control group. No significant difference was found between the study and control groups in terms of blood mercury and lead levels. When the relation of vaccination, the frequency of fish consumption and the number of dental fillings in the mother with blood lead and mercury levels was evaluated, no significant difference was found between the study and control groups. Conclusions: Our study shows that the heavy metal levels of children with chronic neurodevelopmental diseases are not different from those of healthy children. Yet this conclusion does not lower the significance of enviromental heavy metal hazard on human health.