Our aim was to study the impact of preterm birth and neonatal therapies on the risk of childhood cancer using a nationwide, registry-based, case-control design. Combining population-based data from Finnish Medical Birth Registry (MBR) and Finnish Cancer Registry (FCR), we identified a total of 2029 patients diagnosed with cancer under the age of 20 years and 10 103 age- and sex-matched controls over the years 1996-2014. Information on the pre- and perinatal conditions was obtained from the MBR. Gestational age was categorized into early (<32) and late preterm (32-36) and term (≥37 weeks). Cancer risk among the preterm compared to term neonates was evaluated using conditional logistic regression. We identified 141 cancers among the preterm (20.8% of 678) vs 1888 cancers in the term children (16.5% of 11 454). The risk of any cancer was increased for the preterm (OR 1.28, 95% CI 1.06-1.57), especially for the early preterm (OR 1.84, 95% CI 1.16-2.92). The risk of AML (OR 2.33, 95% CI 1.25-4.37), retinoblastoma (OR 3.21, 95% CI 1.22-8.41) and germ cell tumors (OR 5.89, 95% CI 2.29-15.18) was increased among the preterm compared to term. Germ cell tumors were diagnosed at a significantly younger age among the preterm. Neonatal therapies, for example, mechanical ventilation, were associated with an increased risk of childhood cancer independent of gestational age. Preterm, especially early preterm birth is associated with an increased risk of childhood cancer, especially germ cell tumors and AML. Respiratory distress requiring neonatal intervention also appears to be associated with an increased risk.This article is protected by copyright. All rights reserved.