A data-driven, transdiagnostic approach was used to identify the cognitive dimensions linked with learning in a mixed group of 805 children aged 5 to 18 years recognized as having problems in attention, learning, and memory by a health or education practitioner. Assessments included phonological processing; information processing speed; short-term and working memory; executive functions; and attainments in word reading, spelling, and math. Data reduction methods identified 3 dimensions of phonological processing, processing speed, and executive function for the whole sample. This model was comparable for children with and without attention-deficit/hyperactivity disorder (ADHD). The severity of learning difficulties in literacy was linked with phonological processing skills, and in math with executive control. Associations between cognition and learning were similar across younger and older children and individuals with and without ADHD, although stronger links between learning-related problems and both executive skills and processing speed were observed in children with ADHD. These results establish clear domain-specific cognitive pathways to learning that distinguish individuals in the heterogeneous population of children struggling to learn.