Following linkage between the NSW Central Cancer Registry (CCR) and the NSW Midwives Data Collection, an investigation of the association between maternal smoking during pregnancy and the risk of childhood cancer in their offspring was undertaken. Children born in NSW between 1994 and 2005, inclusive of 1,045,966 babies, were matched to 948 cancer cases in the CCR. After adjustment for maternal age, gestational age, baby's gender, birth weight, remoteness index, socioeconomic disadvantage and maternal health factors, no association (OR = 0.96, 95% CI 0.81-1.15, p = 0.68) was found with childhood cancer between mothers who smoked (81/100,000) and those who did not smoke during pregnancy (99/100,000). Maternal smoking was, however, significantly associated with retinoblastoma (OR = 2.20, 95% CI 1.19-4.09, p = 0.01). Association between maternal smoking and preterm birth and low birth weight was significant. Maternal smoking during pregnancy is significantly associated with retinoblastoma and adverse birth outcomes. These results should be highlighted to expectant mothers through antitobacco-smoking campaigns.