Substance abuse is an important health issue facing children involved with child welfare, but little is known about the associated factors. The purpose of this study was to build on findings from the "Canadian Incidence Study of Reported Child Abuse and Neglect-2003" and use a national sample of 10-15 year old children to examine the factors associated with substance abuse for all investigations and substantiated investigations of maltreatment. Our findings showed that almost 14% of all investigated children were abusing substances and that this proportion was even greater among those whose investigation of maltreatment had been substantiated (almost 16%). The severity of the experienced maltreatment, in addition to behavioural factors, was found to be associated with substance abuse. While the pathways to substance abuse are complex, understanding the risk factors associated with substance abuse in this population are important for targeted interventions for prevention and treatment.