The relationship of visual P3a to age was investigated in a life-span sample. The aims of the study were (1) to assess to what extent P3a, relative to P3b, decreases with increasing age; (2) To assess at which recording sites the relationship between P3a and age is strongest; (3) to investigate whether the relationship between P3a and age is best described as linear or nonlinear. One hundred and three well-functioning adults, 20–92 years old, were given a health interview, a battery of neuropsychological tests, and performed a visual three-stimuli oddball ERP task yielding both a P3a and a P3b. P3a and age was moderately correlated, with coefficients reaching .53 (Cz) and −.52 (Pz) for latency and amplitude, respectively. P3b was to a much lesser extent related to age. Generally, the age–P3a relationship was strongest at midline and central electrodes. Finally, the relationship between age and P3a was best described as linear. P3a seems selectively more impaired with age than P3b, but this impairment seems less pronounced at Fz than at Cz and Pz. There is a need for complex theoretical integration of these and previous findings.