In the past few years, synthetic cannabinoid products have been increasingly used by adolescents and young adults. These products are marketed as herbal or aromatic incense and potpourri, but their psychoactive properties appear to be due to the addition of synthetic cannabinoids. When smoked, they can produce significant psychoactive and physical effects similar to cannabis. Changes in cognition, behavioral disturbances, alterations in mood, and perceptual changes have been reported. An emerging body of literature indicates that use of these products is associated with anxiety and other negative mood changes not typical of cannabis intoxication. Use of synthetic cannabinoid products has been associated with new onset psychosis or exacerbation of pre-existing psychosis, although current evidence cannot establish a definitive link between synthetic cannabinoids and psychosis. Clinicians should suspect synthetic cannabinoid product use if a patient: 1) presents with signs and symptoms consistent with cannabis use, 2) has negative routine urine toxicology screens, 3) is in a situation in which his or her urine is being routinely monitored for illicit substance use, and/or 4) presents with otherwise unexplained sudden onset psychosis. To make the diagnosis, clinicians should become familiar with the effects of synthetic cannabinoid use and have a high index of suspicion.