Objective:  This study compares working memory and fluid intelligence in children with three ADHD subtypes. Method: Forty ADHD children ageing 7 to 11 years old were recruited using a cluster random sampling method. CSI-4 symptoms questionnaire, Wechsler intelligence test for children, Cattell's intelligence Test were used to measure ADHD, working memory, and fluid intelligence respectively. Result:  The results of ANOVA, Tukey, and Kruskal-Wallis tests revealed a positive relationship between working memory and fluid intelligence, also there was a difference between the three children groups in working memory and fluid intelligence variables. Conclusion: This research suggests that a relationship exists between working memory and fluid intelligence and ADHD.