Fetal alcohol spectrum disorder (FASD) has been recently estimated to afflict up to 5% of American children. Most of these children exhibit different degrees of symptomatology of disruptive behaviors. Yet, there has been very little research on the efficacy and safety of pharmacological modalities, limited mostly to stimulants for attention deficit hyperactive disorder or second generation atypical antipsychotics for aggression. Recently, the use of cannabinoids has been described for symptoms related to autistic spectrum disorder with apparent favorable effects, as well as for other disruptive behaviors. The objective of our study was to follow up in a retrospective case series the effect of cannabis in children and young adults diagnosed with FASD. In two children and three FASD young adults with severe disruptive behavior, changes in behavior after cannabis use were measured by the parent version of the Nisonger Child Behavior Rating Form. In all five cases, there was a highly statistical decrease in the disruptive behavior score from 18±1.0 before cannabis use to 6±2.1 after introduction of cannabis (=0.0002). In children and young adults with FASD, cannabis, mostly cannabidiol (CBD), has been associated with a marked and statistically significant improvement in serious disruptive behavior. These cases suggest that the efficacy and safety of CBD should be tested in well-controlled studies.