Currently, Brazil has no estimates for quality of life, and/or utilities for ADHD economy analysis. Such data is necessary to calculate the QALYs (Quality Adjusted Life Years). Thus, the investigators will implement the Health Utility Index tool (HUI) to be completed by the patient and/or family, in two moments of an observational study with immediate-release methylphenidate: at baseline and 6th month of treatment. The determination of the QALY as an outcome in the decision analysis is justified because HUI incorporates into a single measure morbidity and mortality. The results of the cost-effectiveness study will assist government agencies in the process of decision making.