The ‘Theory of Visual Attention’ quantifies an interindividual’s capacity of attentional resources in parameters visual processing speed C and vSTM storage capacity K. Distinct neural markers of interindividual differences in these functions were identified by combining TVA-based assessment with neurophysiology: Posterior N1 amplitudes were lower for participants with higher relative to lower processing speed and correlated with individual C-values and CDA was larger for participants with higher relative to lower storage capacity and correlated with individual K-values. When the approach was extended to investigate neural underpinnings of age-related changes in attentional capacities, the ERP markers of individual differences in processing speed and storage capacity were validated also in the older group. Furthermore, additional components were related to performance exclusively in elderly: Anterior N1 amplitudes were reduced for slower older (relative to younger and faster older) participants and correlated with C-values only in the older group. High-storage capacity older (relative to younger and low-storage capacity older participants) obtained a stronger right-central positivity, which correlated with K-values only in the older group. Our findings specify age-related reorganization of attentional brain networks underlying decline and reserve and furthermore show that the distinctiveness of both functions is preserved (or even increased) in older age.