The developing brain is susceptible to the effects of exogenous cannabinoids both during the perinatal period through maternal cannabis use and in young adolescent users. Emerging data from human and animal perinatal exposure studies demonstrate a subtle rather than gross effect of cannabis upon later functioning including; specific cognitive deficits especially in visuospatial function; impulsivity, inattention and hyperactivity; depressive symptoms; and substance use disorders. From animal studies motor control systems, neuroendocrine function and nociception may additionally be affected. Fetal studies indicate that these outcomes may be through cannabinoid mediated influences on the ontogeny of, especially dopamine and opioid, neurotransmitter systems. The effect of cannabinoids in the adolescent suggest long-term deleterious outcomes in cognition, depressive symptoms, schizophrenia and substance use disorders. Much of these data support a neurodevelopmental effect, however, predisposing genetic and/or environmental factors cannot be excluded from human studies. Gender specific differences have been observed in both human and animal studies implying sex hormone and related factors may interact with cannabinoids in neurodevelopment. Further understanding how cannabinoids influence neurodevelopment will inform public debate about the health effects of cannabis but also open avenues in discerning how modulation of the endocannabinoid system may assist in the development of therapeutic tools for a variety of neuropsychiatric disorders.