Children with refractory focal epilepsy differ from adults, although many centers will offer invasive electroencephalography (iEEG) to both. Outcomes in terms of likelihood of resection and subsequent seizure outcome after either subdural grid electrode implantation (SDE) or stereoelectroencephalography (SEEG) have, however, not been directly compared between age groups. We retrospectively included adults and children undergoing iEEG monitoring at four European centers. We compared the two age groups and techniques regarding complication rate, chance of proceeding to resection, and seizure freedom. In total, 857 individuals were included (447 SEEG, 410 SDE; 572 adults, 285 children). Adults more often had a history of focal to bilateral tonic-clonic seizures (FBTCS) and prior epilepsy surgery and were more often magnetic resonance imaging-negative. Children had a higher seizure frequency and rate of preexisting neurologic deficits. In SEEG, likelihood of resection was 64% in adults and 76% in children (p < .05), but chance of seizure freedom did not differ. Adults and children had similar chances of resection and seizure freedom rates after SDE. In children, postoperative seizure freedom was less likely after SDE than SEEG. In adults, history of FBTCS was associated with lower chance of seizure freedom. Overall complication rate was higher in children (22% vs. adults 15%) and in SDE (29% vs. SEEG 7%). Either iEEG technique provides an equally valid but very different road to success, with no difference in seizure outcome between the two age groups, but with higher risk of complications in SDE. We found similar surgical results for dissimilar techniques and a higher threshold for children. In case of an assumed lower chance of focality of epilepsy or chance of seizure freedom after resection, adults were more often explored with iEEG, whereas children were more severely affected when considered for iEEG.