The purpose of this study was (1) to examine the level of learning disabilities reflected in the written expression and writing performance of at-risk children with ADHD, (2) to investigate the level of differences in writing learning disabilities and writing performance depending on ADHD subtypes, and (3) to explore the error types and contents in the written expression of at-risk children with ADHD. The participants in this study were 46 upper grade elementary school children. They were firstly screened by teacher nomination, and only participants with a K-ARS score of over 17 were then selected to be among the 46 children involved in this study. Two further tests were then carried out : K-LDES as an index of learning disabilities in written expression and BASA-writing as an index of writing performance. The results showed that the at-risk children with ADHD possibly had comorbid writing learning disabilities. They were significantly different in terms of the number of total syllables, errors and correct syllables that they produced, in comparison to normal children. But there were no differences as regards the level of learning disabilities in terms of written expression and writing performance based on ADHD subtypes. As regards the implications of these results for future research, we suggested that there is a need for the identification of comorbid writing learning disabilities in ADHD assessment.