Objective: Schizophrenia generally has cognitive impairments. So, cognitive impairments can affect whole life's aspects, cognitive assessment helps develop treatment planning and obtain independency in occupational performance areas. The goal of this study is supporting construct validity of the Iranian version of lowenstien occupational therapy cognitive assessment (LOTCA) through Comparison of cognition among psychiatric patients and general population.Material & Methods: This is a cross sectional study on 737 person (237- patient & 500- general population) in 20-60 age. Samples select accordance to research criteria. The tool was Lotca that asses six cognitive areas. Data gathered through demographic questionnaire and Lotca's scoring sheet and analyzed by, T-test, Leven and correlation tests. Results: There was meaning different between cognitive performance of schizophrenic patients and normal population (P<0.05). Comparison of cognitive performance of inpatients and outpatients showed significant difference in orientation, visual perception, attention and concentration (P<0.05). In females Thinking operations, attention and concentration was higher than males. The mean of scores of subscales in employed person significantly were higher than unemployed persons. Subscales scores has reduced with increasing of age. Married persons showed higher orientation. Also there was significant difference between level of education and desirability of seven subscales.Conclusion: Results show significant differences between schizophrenic patients and general population on almost all sub tests of the LOTCA, supporting construct validity for assessing, planning of interventions and adaptation of environment in the schizophrenic patients.