The paper by Yoo et al. (1) draws attention to the significant numbers of unexpected infant deaths that are occurring in shared sleeping situations. It is now well-recognized that the more comprehensively cases of unexpected infant death are investigated, the greater is the number of cases where deaths are attributed to something other than sudden infant death syndrome (SIDS) (2, 3). However, although bed sharing deaths are still often universally attributed to SIDS (1, 4), the possibility of an asphyxial mechanism of death in some cases must be recognised (5, 6). In support of this, a recent study in South Australia demonstrated that the male to female ratio in infants who died alone was approximately 2:1, as is typical of SIDS deaths. This was significantly different to the sex ratio of infants who died in shared sleeping situation which approached unity (7). One explanation for this marked difference is that although females are less vulnerable to SIDS than males, this protection does not extend to situations where lethal asphyxia may occur; i.e. gender does not protect an infant from accidental suffocation, or so-called 'overlaying'. A more detailed description of the nature of shared sleeping arrangements in Korea from the authors would be a useful addition to their data, in addition to a comparison of the sex ratio of the alone and shared sleepers, to see if the usual SIDS male to female ratio is present, or not, in this population.