This comparative study investigated the productivity and the process of written composition in students with and without disabilities between 8 and 16 years of age. Participants were assigned to four groups as follows: (a) 59 with both attention-deficit/hyperactivity disorders (ADHD) and writing learning disabilities (WLD), (b) 40 with ADHD, (c) 115 with WLD, and (d) 124 normal achievers (control group). Students' writing productivity was assessed by means of a compare-and-contrast essay task and a writing log that registered the processes involved in composition writing using seven categories. The findings render insight into the way children and youth with ADHD and WLD produce text and how much time they dedicate to the various writing subtasks. Among other things, students with ADHD and WLD spend much less time than normal peers thinking about a written composition or reviewing it, which negatively affects the level of coherence and quality of their texts. A critical discussion of the findings and their psychoeducational implications is included.