The aim of this research was to investigate the differences in severity of symptoms of autism in children with diagnosed autism spectrum disorder and level of percieved parental stress in families with and without a service dog. The participants were 53 parents of children with disgnosed autism spectrum disorder, 17 of which had a service dog for child with autism in their family, and 36 did not have a service dog. Instruments used in this research were Autism Quotient and Parental stress scale (Berry & Jones, 1995). Autism Quotient was used in versions for children (Baron-Cohen et al, 2006) and adolescents (Auyeung et al, 2008). A statisticaly signifficant difference was found between the children with ASD, when the owning of a service dog was considered. In other words, children with ASD who own a service dog exhibited less symptoms of ASD than children who do not own a service dog. Also, statisticaly signifficant difference was found in subscales Communication and Attention to detail, meaning that children with the diagnosis of autism who owned a service dog had better communication and paid less attention to detail than children with ASD without a service dog. However, there was no statisticaly signifficant difference on subscales Social skills, Attention switching and Imagination, nor in perceived parental stress in families with and without a service dog. No significant correlation between symptoms of autism in children with diagnosed autism spectrum disorder and level of percieved parental stress was found. The results indicate the benefits of having a service dog in families with children with autism spectrum disorder.