Hypothalamic hamartomas (HHs) are intrinsically epileptogenic lesions associated to medically intractable focal epilepsy mainly characterized by gelastic and focal seizures. Intralesional recording with deep electrodes has documented the presence of ictal discharge arising from inside the lesion. Nevertheless interictal and ictal scalp EEG is poorly informative and non-localizing in a great deal of cases. HH disconnection leads to seizure remission in most cases. To describe the intralesional EEG recordings and to compare them with concomitant scalp EEG and with previous cases reported in literature. We reviewed the medical records of 17 children affected by drug-resistant focal epilepsy associated to HH. We recorded intralesional electrical activity during stereo-endoscopic disconnection in three cases and during deep brain stimulation implantation in one. We also correlated it with the simultaneous scalp-EEG recording. Acute intralesional recordings in our cases confirmed the presence of epileptiform abnormalities intermingled with low-voltage activity, mostly on the same side of the HH attachment. Paroxysmal activity recorded inside the HH was always evident. Mapping of HH epileptogenic activity could be useful to confirm the usefulness of disconnection procedure. This should consider on-site recording from the HH and if abnormalities are detected safely proceed to disconnection of the HH.