Introduction: Long-acting stimulant formulations are recommended as first-line pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD). Over the past 20 years, extended-release (ER) methylphenidate (MPH) and amphetamine (AMP) formulations have evolved to include varying drug delivery technologies, enantiomers/salts, and dosage forms. All formulations are characterized by a unique pharmacokinetic profile that is closely mirrored by pharmacodynamic response allowing clinicians to individualize therapy based on their patient's clinical needs and dosing preferences. Areas covered: This review provides an update on the pharmacokinetic properties of approved and investigational ER MPH and AMP formulations and highlights pharmacokinetic features that clinicians should consider when selecting a long-acting stimulant. Expert opinion: Since there are no reliable biomarkers that can predict individualized response to long-acting stimulants, clinicians need to consider their distinctive pharmacokinetic properties, including the pharmacokinetic profile, rate and extent of absorption, variability, dose proportionality, bioequivalence, and potential for accumulation. Clinicians also need to understand that certain factors can contribute to increased variability in pharmacokinetics and potentially affect outcomes. Less invasive, high-throughput techniques and novel time-based scales are being developed to advance research on the pharmacokinetic-pharmacodynamic relationships of stimulants. Model-based pharmacokinetic-pharmacodynamic approaches can be applied to aid the development of novel formulations and individualize therapy with existing drugs.