Computerised medical record (CMR) system data can be used to compare different models of health care for children. We identified sources of data from the Models of Child Health Appraised (MOCHA) project that compares family doctor led with paediatrician led and mixed models of child care using index conditions. Asthma and immunisation coverage are the first of these. We explored the extent to which an established Patient Registries Initiative (PARENT); MOCHA's own survey (MIROI); the European Centre for Disease Control (ECDC) immunisation information system survey and the European Network of Centres for Pharmacoepidemiology and Pharmacovigilance (ENCePP) registry of data sources provided data to make comparisons of child health care. Five countries had data repositories for our index conditions from paediatrician lead services, compared with 14 for mixed, and 11 for family doctor led services. PARENT identified 212 sources, MIROI 148 sources, ECDC 17 sources and ENCePP 42; with immunisation related data sources found in all four but asthma in only three. There are less sources of electronic data available to study paediatrician led systems than other models; this risks unequal sample size bias.