Researchers have established the importance of single word reading to reading comprehension. However, there is a significant number of children (approximately 3%), predominantly ten years of age and older, who are poor comprehenders, but nevertheless attain scores within the normal range on conventional measures of single word reading, which typically measure accuracy only. We will examine potential sources of poor reading comprehension among children and adolescents by studying subjects with poor single word reading, subjects with poor reading comprehension despite normal scores on tests of single word reading, and controls with typically developing reading skills. We will integrate functional neuroimaging data that examines group differences in activation during single word reading, phonological awareness and sentences reading comprehension, with behavioral measures of naming fluency, language skills (i.e., vocabulary), executive function (i.e., planning, organizing, and self-monitoring), single word reading, phonological skills, and passage reading comprehension.