Background: High incidence of learning disorders has caught the psychologists' attention in recent years. Objectives: The objective of this study was to compare divided, sustained and selective attention in children with attention deficit hyperactivity disorder, children with a specific learning disorder and normal children. Methods: The study was a descriptive, causal-comparative and fundamental research. The population consisted of all children with attention deficit hyperactivity disorder (ADHD) and children with specific learning psychology (SLD), aged 7 to 12 years old, who referred to counseling and psychiatric clinics in Tehran in 2016, as well as normal primary school children. 36 children with attention deficit hyperactivity disorder and 47 children with specific learning difficulties were selected through convenience sampling, and 43 ordinary primary school children with cluster-randomly sampling method. Continuous performance test, word color Stroop test and the Wechsler scales were used as the instruments of the study. Descriptive and inferential statistics along with multivariate analysis of variance in Spss-21were used to analyze data. Results:The results of this study showed that weakness in divided, selective and sustained attention in children with attention deficit hyperactivity disorder and children with specific learning disorder is more than normal children (P < 0.05). However, there was no significant difference between these variables in children with attention deficit hyperactivity disorder and children with specific learning disorder (P < 0.01). Conclusions:The results showed that the rate of comorbidity was very high in children with attention deficit -hyperactivity disorder and children with specific learning disorder.