An increasing number of chronically ill children enter adulthood due to advances in diagnosis and treatment. Overall, chronically ill children are at a greater risk of oral health problems than healthy children. The need for hospital treatment and inadequate oral hygiene, malnutrition, and the effect of medications can contribute to the development of oral cavity diseases. In addition to the increased risk for oral cavity diseases, some chronic diseases such as chronic inflammatory bowel diseases, eating disorders, diabetes type 1, and celiac disease, can be recognized by changes in the mucous membrane of the oral cavity. Ulcerative lesions, chronic tonsillitis and orofacial granulomatosis can be the first manifestations of Crohn's disease. Changes in the oral cavity in patients with eating disorders can be the result of malnutrition and self-induced vomiting and include enamel erosion, caries, and changes in the amount and composition of saliva. The first sign of celiac disease can be recurrent canker sores in the mouth, damage to the enamel of permanent teeth, and often glossitis and caries. Children with celiac disease type 1 have a higher risk for periodontal disease, xerostomia, and candidiasis. Dental procedures in these children require extensive knowledge of disease control while planning the procedure depending on meal intake and insulin therapy. Children with congenital heart defects may be more susceptible to the development of oral diseases due to malnutrition and the effect of medications. Certain groups of these children require special supervision and care for oral health due to the risk of infectious endocarditis. The performance of certain dental procedures in these children requires the use of infective endocarditis prophylaxis. Dentists play a key role in recognizing the signs of chronic diseases and their treatment in children, which can contribute to preserving the health and improving the quality of life.