QUESTIONS UNDER STUDY: Completeness is important in cancer registration. Identifying areas to improve registry procedures might help to maximise completeness. We examined characteristics of childhood cancer cases that were registered via death certificate notification (DCN) rather than during life, and estimated completeness of the Swiss Childhood Cancer Registry (SCCR). METHODS: We analysed data from all children who died from cancer in Switzerland between 1985–2009 at age <16 years (n = 978), and checked whether they had been registered in the SCCR. We used multivariable logistic regression to compare characteristics of DCN cases with deceased SCCR cases, and the DCN-to-incidence and mortality-to-incidence ratio method to estimate completeness for different diagnostic periods. RESULTS: Among 978 deceased children with cancer, 126 (12.9%) were registered via DCN. Those with tumours of digestive organs (odds ratio [OR] 5.1; 95% confidence interval [CI] 1.9–13.7), tumours of endocrine glands (OR 4.5; 95% CI 1.6–12.3), and brain tumours (OR 3.1; 95% CI 1.7–5.5) were more likely to be DCN cases than those with leukaemia. Neonates (OR 14.1, 95% CI 5.3–37.3), infants (OR 7.5; 95% CI 3.1–18.0) and 14–15 year olds (OR 2.4; 95% CI 1.2–4.9) were more likely to be DCN cases than 1–4 year olds. The DCN proportion was particularly high in infants who lived in rural regions. Estimated completeness of the SCCR increased from 85% for 1985–89 to ≥95% for 1995–2009. CONCLUSIONS: Childhood cancer registration in Switzerland was quite complete, but registration must improve for infants, particularly neonates, and children diagnosed with hepatic, endocrine and brain tumours.