This online study explored the relationship between maternal Posttraumatic Stress Disorder (PTSD) and level of substance use (SUD) in a population of 402 adult children of Holocaust survivors (CHS) recruited from online support groups serving the Jewish community.   Previous research has demonstrated a relationship between PTSD and SUD comorbidity.  The perception of maternal PTSD and levels of alcohol and/or drug use in offspring were examined using the SMAST, DAST, The Parental Posttraumatic Stress Questionnaire (PPQ) and the PTSD Checklist (PCL-C).  The results confirmed that offspring with higher levels of their own PTSD also rated their mothers as having higher levels of PTSD.  In total, 40.4 % of CHS met DSM-IV criteria for current PTSD and 60.4% rated their mothers as having a DSM-IV PTSD diagnosis.   Offspring also rated their mothers as having problems with anxiety (81%), depression (70.3%) mood altering-prescription medications (18.5%) and alcohol (2.9%).  CHS that rated their mothers as having higher levels of PTSD also had significantly higher levels of their own alcohol and drug use.  More than twice as many CHS identified a problem with drugs (13.6%) than alcohol (6.1%).  These findings confirm high prevalence rates of PTSD in Holocaust survivors and their offspring.   It also suggests that the intergenerational transmission of maternal PTSD is a possible risk factor for SUD in the second-generation of trauma survivors.