The Smith-Lemli-Opitz syndrome (SLOS) is a congenital, genetically conditioned, metabolic disorder with autosomal recessive inheritance. The syndrome is caused by high levels of cholesterol precursors, i.e. 7-dyhdrocholesterol (DHCR7) and 8-dehydrocholesterol (DHCR8), which results in cholesterol synthesis disorders. Cholesterol deficiency leads to a series of developmental disorders in the foetus and in extreme cases even death. The diagnosis of that congenital metabolic disorder is difficult due to a diversity of clinical symptoms (there are many mutations of the DHCR7 and DHCR8 genes), which can be exemplified by such cases as that of the 5-year-old boy with SLOS described below. In the presentation the authors have emphasized the problems related to hygienic procedures of the oral cavity and dental treatment, as well as the importance of the early diagnosis of the syndrome and of cooperation with parents. The publication aims at drawing the attention of clinicians to the need of taking SLOS into account in the differential diagnostics in children.