Infantile Epileptic Spasms Syndrome (IESS) is an age-related developmental and epileptic encephalopathy that may be resistant to treatment and can negatively affect neurodevelopment. The classification of the etiology of IESS is important for its treatment, considering prognosis, and for future studies. The present study aimed to investigate the difficulties in etiologic classification of IESS based on the International League Against Epilepsy (ILAE, 2017). The data of patients diagnosed with IESS between 2014 and 2023 were reviewed retrospectively. The diagnosis of IESS was made by the presence of epileptic spasm and/or hypsarrhythmia on electroencephalography (EEG). Etiological classification was made based on the 2017 (ILAE) etiologic classification and the difficulties encountered were examined. In this study, 108 patients, 63 (%58) girls and (%42)45 boys, with a mean age of 22±13 (3-72) months, were included. The etiology remained unclear in 30 patients (27.7%) and was detected in 78 patients (72.2%). The underlying causes of patients were genetic 16 (14.8%), structural 57 (61.5%), inherited metabolic diseases 4 (3.7%), and infectious 1 (0.9%). Congenital metabolic diseases were included in the metabolic diseases group. Since different etiologies could cause IESS, either alone or in combination, difficulties were encountered especially in grouping the patients with a genetic origin of the disease, resulting in structural anomalies and inherited metabolic diseases. The basic difficulty encountered during the ILAE classification of this large group of patients was to classify the genetic causes that result in structural anomalies and congenital metabolic diseases. Previous experience, along with the findings of the present study, suggest that ILAE 2017 etiologic classification may be revised, genetic reasons resulting in structural and/or metabolic abnormalities should be classified under the name of genetic origin and that genetic titles should be divided into subgroups such as genetic metabolic, genetic structural, and other genetic categories.