Abstract: The invention provides a method for the treatment of certain psychiatric disorders using entacapone, tolcapone and other COMT inhibitor drugs or MB-COMT inhibitor compounds. The method is effective in particular for improving positive and negative symptoms of Schizophrenia (SCZ), major depression, the depressive phase of Bipolar Disorder (BD) and substance dependency. The method can also be used as a treatment to combat cravings associated with abuse of alcohol, opiates, cocaine, marijuana, amphetamines and Tobacco addiction. In addition to these diseases it is useful for the treatment of ADD/ADHD, cognitive enhancement in head injuries and dementias.