The aim of the proposed pilot study is to find out whether varenicline treatment decreases alcohol use and smoking in patients with schizophrenia or schizoaffective disorder. Varenicline may also improve cognition (memory and concentration) and negative symptoms (e.g. poor attention, poverty of speech, apathy, affective flattening, anhedonia) in patients with schizophrenia and comorbid nicotine and alcohol dependence.