The relation between brain and mind is quite evident. Neuropsychological instruments have made considerable contributions in evaluating cognitive functions among healthy individuals and those patients suffering from psychiatric and brain syndromes. In this research, Stroop and Benton neuropsychological assessments have been used. Stroop test is a common test to assess executive functions, selective attention and concentration. In that test, the subject should state the color of words which have been written in various colors without consideration of their meanings. The test is also used to assess frontal lobe. Benton test is used to assess visual memory, visual perception and visual organization capability. Qualitative interpretation of the results of this test provides useful information concerning the type and possible location of brain lesion in those who are suspected to brain lesion. In the present research, performances of people with schizophrenia, bipolar patients and ordinary people have been compared by the aforesaid two tests. One of the scientific goals of this research is to compare visual memory, cognitive memory and fundamental capabilities as well as the function of frontal lobe in schizophrenia and bipolar patients and ordinary people. One of the practical goals of this research is that by using Stroop and Benton neuropsychological tests, we can better understand the function and severity of cognitive defects in schizophrenia and bipolar patients and ordinary people and we can use the obtained findings in treating schizophrenia and bipolar patients. By using this research, we will know the exact place of brain lesions and traumatic brain injuries. Research findings will lead us to better treatment of schizophrenia and bipolar patients. Statistical methods in this research are of post-event (causal-comparative) type. Available cluster sampling method has been selected by which 30 schizophrenia patients, 30 bipolar patients and 30 ordinary people were selected and their performances were compared by using Benton and Stroop tests. Results in this research indicate that performance of schizophrenia and bipolar patients in Benton and Stroop tests did not differ significantly; however, it was significantly different from ordinary people. Results of the present research indicate that schizophrenia and bipolar patients have defective frontal lobe. In this way, although schizophrenia and bipolar disorders are two separate issues in psychiatry, they can be closed in neuroanatomical, neurochemical and psychopharmacological levels. The results of studies conducted in abroad in this regard conform to the results obtained in this research. In this research, performances of schizophrenia and bipolar patients did not differ so much and were close, but the performances of the two groups in the two tests were significantly different from the performance of ordinary people.