A study of prevalence and aetiology was performed on 63 children and 127 adults in Denmark with congenital deafblindness. Using a Scandinavian definition of deafblindness, the prevalence of congenital deafblindness was found to be 1:29,000. Thirty-five different aetiological causes of deafblindness were found. Causes of congenital deafblindness were different among adults compared to causes among children. Rubella syndrome (28%, n = 36) and Down syndrome (8%, n = 10) were the largest groups among people above 18 years of age. Among children CHARGE syndrome (16%, n = 13) was the largest group. Ethnicity was also evaluated. Among children 72% were Danish, but among the adults 98% were Danish. Implications of difference in aetiology and ethnicity are discussed in relation to the Scandinavian traditions of clinical practice and identification of congenital deafblindness.