Introduction & Objective: Glioma is a kind of CNS tumor, originated from glial cells. CNS diseases can present with Sensory-Motor, Cognitive or psychological dysfunctions. Dysfunction in sensory-motor domain can be measured with standard physical examination and Para clinics, but evaluating dysfunction in cognitive and psychological domains are usually more complicated. Materials & Methods: 30 patients with dominant hemisphere gliomas, operated in Sina hospital were assessed in this study. They were undergone cognitive examination with Addenbrooke’s Cognitive Examination (ACE) pre operatively, post operatively and 3 and6 months after surgery. Results: Before Surgery, mean cognitive function mark before surgery was 74.2±16.78. Just post operatively mean cognitive function mark slightly dropped to 64.17±18.2 but this drop wasn’t statistically meaningful. 3 months after surgery, patients’ cognitive function got better and reached 74±16.61 and 6 months after surgery, mean cognitive function mark in patients, reached 82.76±12.9. This improvement at 6 months after surgery in comparison to just post-operative status was statistically significant. Conclusions: In pre-operative assessment, 83.3% of patients have some degrees of cognitive dysfunction. This makes cognitive dysfunction, a significant sign of gliomas. Although post operatively we observed a slight decline in cognitive function, but in 6 months, most patients significantly recovered.