Congenital hypothyroidism (CH) may be of thyroidal (CHT) or central origin (CHC). Worldwide, most neonatal screening programs are TSH based and effectively detect CHT. Only a few screening programs measure total or free T4 and TSH simultaneously or stepwise, enabling detection of CHT as well as CHC. A frequently used argument against screening for CHC is its presumed mild hypothyroid character. In the recently published European Society for Paediatric Endocrinology (ESPE) CH consensus guidelines on screening, diagnosis and management, severity of CH is classified based on initial free T4 (FT4) concentrations. Objective: To assess disease severity of CHC compared to CHT in a Dutch cohort of CH patients. Methods: Pre-treatment FT4 concentrations were analyzed in all children with CH detected by the Dutch neonatal T4+TSH+T4-binding-globulin (TBG) screening between 1995 and 2011. Disease severity was classified using the FT4-based ESPE classification. Results: Between 1995 and 2011, 1288 children were diagnosed with CH. Data of 1200 (CHC: 143, CHT: 1057) were available for analysis. Based on FT4 concentrations 4 children with CHC (2.8%) had severe CH, 75 (52.4%) moderate and 64 (44.8%) mild. In the CHT group 280 children (26.5%) had severe CH, 341 (32.3%) moderate and 436 (41.2%) mild. Discussion:/Conclusion /Conclusion: Our results indicate that, based on initial FT4-values, severe CH was much more prevalent in CHT compared to CHC. However CHC itself should not be considered as only mild since more than half of CHC patients have moderate CH with initial FT4 below 10 pmol/l.