The Triangle Model of Reading proposes that phonology, orthography, and semantics are crucial to understand word reading and reading disability (RD). Morphology has been added as a binding agent to this model. However, it is unclear how these variables relate to word reading in children with attention deficit/hyperactivity disorder (ADHD) or comorbid ADHD and RD (ADHD+RD). This study examined the performance of Chinese children with RD, ADHD, or ADHD+RD in phonology, orthography, semantics, and morphology, and investigated whether morphology made an additional contribution beyond the other skills in explaining word reading fluency. Participants were 151 Grade 1 to 3 Chinese students: RD (n = 31), ADHD (n = 43), ADHD+RD (n = 27), and typically developing controls (TD, n = 50). Results indicated that children with ADHD+RD (a) showed similar performance to RD and ADHD in tone awareness, orthographic legality, and homophone morpheme awareness; (b) had similar performance to RD but worse than ADHD in phonology, semantics, and morpheme production; and (c) had more severe deficits than RD and ADHD in orthographic reversal, morpheme identification, and homograph awareness. Morphology significantly predicted word reading fluency beyond the other skills, and its predictive effect was more salient for ADHD+RD, ADHD, and TD. The findings provide evidence of both shared and additive effects of RD and ADHD. Morphology may be an important diagnostic factor in identifying Chinese reading and behavioral deficit groups and a worthwhile target for intervention.