The aim of the study was to identify differences in occurrence of gastrointestinal (GI) abnormalities for children with Autism Spectrum Disorder (ASD) and children with typical development as well the most commonly occurring GI symptoms and food allergies, dislikes and diet restrictions for both groups of children. The study further examined relationships between severity of these problems and severity of ASD, insomnia symptoms and parental stress. A total of 247 parents of children living in Ireland participated in the study. Results indicate that insomnia symptoms predict ASD severity and parental stress regardless of type of development. GI symptoms predict sleep problems. Inconclusive results were obtained for food allergies, dislikes and diet restrictions. Higher frequency of insomnia symptoms and GI symptoms, mainly abdominal pain, gaseousness/bloating and constipation, were found for children with ASD. Parents of children with ASD reported higher level of stress than parents of children with typical development.