The consequences of febrile seizures (FSs) in infants are still a matter of debate. It is important to develop non-invasive tools to determine markers of brain function that could have predictive value for the outcome of FSs infants.Pattern visual evoked potentials (pVEPs) were recorded in 18 FS infants (mean age of seizure 15.97 months). Spectral density and coherence analyses were performed in infants evaluated at 1.1 month (n = 4), 5.75 months (n = 4) or 30.33 months (n = 6) following a prolonged FS and compared to age-matched healthy controls. The impact of severity of seizures was assessed by comparing the children who had prolonged FSs to 4 infants that had experienced a simple FS. Cognitive tests (Bayley, Stanford-Binet) were administered at the time of testing in FS and control children. Behavioural measures (Achenbach Child Behavior Check List) were administered two years after the FS. pVEP responses and coherence measures failed to yield significant differences between the FS groups and healthy controls. However, spectral density measures showed a significant increase in delta band activity in both FS groups and a reduced high frequency density only in the prolonged FS groups that was seen up to 39 months post-seizure. Behavioural and cognitive measures revealed cognitive development within average, but lower attentional capacities in the FS infants. The persistent changes in spectral density patterns seen in children with prolonged FS may reflect seizure induced alterations in the developing brain or a result of a complex mode of inheritance. Further studies are needed to determine whether these observations can be used as a marker to predict the vulnerability of the child in developing behavioral deficits or epilepsy.