The smoking of cannabis and tobacco is common in many countries. In contrast to tobacco, which is an established risk factor for the sudden infant death syndrome (SIDS), nothing is known about cannabis and its effects on SIDS risk. We analysed data collected in a nation-wide case control study in New Zealand (393 cases, 1592 controls) to determine if there is any association between maternal cannabis use and SIDS risk. Adjusting for ethnicity and maternal tobacco use, the SIDS odds ratio for >weekly maternal cannabis use since the infant's birth was 2.23 (95% CI = 1.39, 3.57) compared to non-users; and the multivariate odds ratio was 1.55 (95% CI = 0.87, 2.75). We conclude that frequent maternal cannabis use may be a weak risk factor for SIDS, but this finding requires further research.