The purpose of this study was (i) to investigate if the compensatory effect of text-to-speech (TTS) technology on reading comprehension and reading rate in schoolchildren with reading disability is influenced by problems with inattention and hyperactivity and (ii) to examine whether a potentially moderating effect of such symptoms differ between grade groups. Participants (N = 49) were randomized into one of the two experimental conditions: Group A listened to a text with TTS, and Group B read the text themselves. The conditions were then switched. Inattention and hyperactivity symptoms were assessed with the Strengths and Difficulties Questionnaire (SDQ). Statistical analyses were performed both on the whole group and within-grade groups (Grades 3-5 and 6-9). Using TTS technology had a positive effect on reading rate for both grade groups, and this effect was not influenced by attention-deficit/hyperactivity disorder (ADHD) symptoms. As for reading comprehension, the two groups differed both with respect to the amount of improvement seen in the TTS condition and with respect to the moderating effect of ADHD symptoms. Reading with TTS improved reading comprehension significantly in the younger group, whereas no effect on reading comprehension was found in the older group. A higher score on the SDQ ADHD Scale was associated with "less" improvement in reading comprehension in the younger group and with "greater" improvement in reading comprehension in the older group. The results indicate that symptoms of inattention and hyperactivity, as well as the child's grade level, are factors that should be taken into account when planning and introducing TTS technology.