Inclusion Criteria:

1. Schizophrenia or Schizoaffective disorder (DSM-IV SCID-confirmed),
2. Age: 18-55 years
3. Capable of providing informed consent
4. HVLT total immediate recall scores lower (≥ 1 SD) from the mean score in the general population (28.16±1.58) [40] .
5. At least 3 months of treatment with stable doses (no dose change in 4 weeks) olanzapine (10-20 mg) or risperidone (3-6 mg) or long acting Risperidone

Exclusion Criteria:

1. Other current or past DSM-IV Axis I diagnoses that require pharmacological treatment; At the discretion of the investigator, some diagnoses e.g., past adjustment disorders may be permitted.
2. DSM-IV/DSM-IV-TR diagnosis of alcohol or substance abuse (other than nicotine) within the last 3 months or a DSM-IV/DSM-IV-TR diagnosis of alcohol or substance dependence (other than nicotine) within the last 6 months.
3. Serious medical or neurological illness (unstable cardiac disease, AIDS, malignancy, liver or renal impairment, dementia) or treatment for a medical disorder that could interfere with study participation.
4. History of significant head injury/trauma.
5. Women who are pregnant, nursing or unwilling to use appropriate birth control measures during study participation. This is because the effects of CBD on a fetus are unknown
6. Inability to complete neuropsychological tests.
7. Current treatment with quetiapine, ziprasidone, aripiprazole, clozapine or typical antipsychotics (at antipsychotic doses)
8. Current treatment with investigational agents or participation in another clinical trial
9. Current participation in a weight loss program
10. Current treatment with a cognition enhancer
11. Treatment with ECT within the past 2 months
12. Patients on concomitant anticholinergic drugs or benzodiazepines will be required to withhold the dose 4 hours prior to cognitive testing.