This study contributes to the growing child protection placement literature by providing the first Canadian provincial longitudinal study examining when and for whom initial out-of-home placement is most likely to occur. Anonymized clinical-administrative child protection data were merged with the 2006 Canadian Census data for the province of Québec, and the final dataset included 127,181 children investigated for maltreatment for the first time between April 1, 2002 and March 31, 2010. Cox proportional hazard results indicate that the vast majority of investigated children do not experience a placement, but for the others, placement tends to occur immediately following the maltreatment investigation with only a slight increase in risk over time. The increased risk of placement for younger children aged 0 to 9 years was statistically explained by a combination of male gender, behavioral problems, parents' high risk lifestyles, hospital referral, the number of investigations and neighborhood area socioeconomic disadvantages. The increased risk of placement for older children aged 10 to 17 years was statistically explained by a combination of behavioral problems, police reporting, the number of investigations and neighborhood area socioeconomic disadvantages. Neighborhood area socioeconomic disadvantages significantly contributed to the increased risk of out-of-home placement for all children, but this factor is most influential when it comes to younger children.