The solitary median maxillary central incisor (SMMCI) syndrome is a congenital developmental defect of the head. The prevalent symptom is a solitary median incisor of the maxilla both in primary and secondary dentition. The cause of the syndrome is related to the midline defects in the migration and connection of the prechordal mesoderm between the 35th and the 38th day post conception. Such malformation occurs at the region of the frontonasal process which takes part in the formation of the median structures of the head such as the incisive bone with incisors and the corresponding region of the mouth cavity vault, the philtrum and the median part of the upper vermilion border, and additionally eye sockets, nasal ducts with anterior and posterior nares, nasal septum, and the palatal wall. The remaining characteristic features of the syndrome are observed in the head region and also co-exist with other systemic developmental defects. The aim of the study was to present the SMMCI syndrome in two female patients treated at the Department of Orthodontics of the Medical University of Silesia in Zabrze, Poland. Based on the patient observations, the diagnosis is made late, most frequently by dentists after the occurrence of the prevalent symptom. The aim of orthodontists is to monitor the development of dentition and occlusion, detailed radiological investigation and interceptive orthodontic care.