We examined the caries prevalence and treatment needs of medically compromised and healthy paediatric patients attending the dental clinic of a tertiary care institution in Saudi Arabia. The medical records of 175 healthy and 211 medically compromised 5-year-old Saudi children were reviewed. Data was extracted on clinical status and number of decayed, extracted and filled teeth (deft score). A total of 91.9% of medically compromised and 84.0% of healthy children had evidence of caries. Mean deft score was 9.91 for medically compromised and 6.25 for healthy children. A high proportion of carious teeth (79%) were untreated, with no significant difference between the 2 groups.