Calculation disorders, calculation disabilities, or dyscalculia refer to various problems in acquiring calculation skills. The guide provides an overview of the current state of research on the causes, progression, and treatment options for dyscalculia. The guidelines from national professional associations for child and adolescent psychiatry regarding the diagnosis and monitoring of calculation disorders, as well as their treatment, are presented in a practical manner. Possible comorbid neuropsychological impairments, as well as emotional and behavioral disorders, are also taken into account. The therapeutic approach is characterized by educational, neuropsychological, learning, and behavioral therapeutic techniques. The provision of materials for the diagnostic and therapeutic process, along with the illustration of the procedure using case studies, contributes to the improvement of treatment quality.