Given the increasing prevalence and knowledge of autism spectrum disorders (ASD) and inherited metabolic diseases (IMD), the aim of this manuscript was to provide practical implications of the molecular (metabolic) diagnostics of ASD and also give the rationale of selective screening of IMD in paediatric patients presenting with autistic features. A wide range of autistic features have been reported in patients with various IMD, including aminoacidopathies, organic acidurias, cerebral creatine deficiencies, and defects of purines and pyrimidines metabolism. A total of 9 cross-sectional studies reporting children diagnosed with ASD, who were subsequently screened for IMD, were identified. There is no cause-effect relationship be-tween autism spectrum disorders and inherited metabolic diseases; however, all neurometabolic diseases presenting with intellectual disability may meet the criteria for ASD diagnosis.