We present the case of an 11-month-old girl with linear nevus sebaceous syndrome who underwent posterior quadrantectomy(PQ)for intractable epilepsy due to cortical dysplasia extending from the temporal, parietal, and occipital lobes in the right hemisphere. Epileptic spasms started at 4 months after birth, and the frequency of her seizures gradually increased to 10 episodes per day. Electroencephalograms in the interictal periods showed hypsarrhythmia. Magnetic resonance imaging(MRI)suggested cortical dysplasia in the right temporal, parietal, and occipital lobes. Ictal single-photon emission computed tomography revealed increased cerebral blood flow in similar areas as the cortical dysplasia suggested on MRI. Several antiepileptic drugs were administered to control the epileptic spasms, without success. In addition, her developmental delay gradually became evident. Because the epileptic foci extended into the posterior region of the right hemisphere, we did not execute a focused resection, but performed a PQ. The epileptic spasms completely disappeared after surgery and her developmental delay gradually improved. Early surgical intervention via PQ is useful in patients with drug-resistant epilepsy in whom the epileptic foci have extended into the temporal, parietal, and occipital lobes. This intervention not only controls intractable seizures but also helps to facilitate normal development.