We measured event-related potentials (ERP) in a unique lifespan sample to examine age differences in cognitive control. By comparing  stimulus- and response-related cognitive subprocesses across four age groups, we found evidence for age specific challenges in cognitive control. Larger differences between ERPs to critical and less critical inputs (A, NOGO and GO) as well ERPs during critical and less critical responses (B, error and correct) are indicative of a strong cognitive control system. In younger adults (C), we found that control demanding stimulus inputs (A, NOGO, in dark green) as well as responses (B, errors in dark red) are well differentiated in ERPs.In children however (D), control-demanding stimulus inputs could not be translated into a stronger focus to avoid errors. This is also indicated by less differentiated ERP potentials to response outputs (red circle in B).In older adults (E), yet a different challenge is aparent. A reduced ability to strengthen stimulus inputs forces the control system to 'run on half-empty'. ERP potentials related to stimulus inputs as well as response outputs are less differentiated (red circles A and B).