Objective: Inflammation is an important factor in pathophysiology of bipolar disorder. Neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) analysis are used to predict peripheral inflammation. The aim of this study is to calculate neutrophil-lymphocyte and platelet-lymphocyte ratios, which are inflammatory markers, and investigate their effect on cognitive functions in euthymic patients with objective bipolar disorder.Method: Twenty - eight patients with type-I bipolar disorder and 22 healthy controls matched for age, gender and educational status were included in the study. Neuropsychological tests were applied to all participants. Neutrophils, lymphocytes and platelets counts of the participants were measured and NLR and PLR were calculated.Results: There was a significant negative correlation between NLR and Stroop interference score in study group. There was no statistically significant difference in NLR and PLR between study and control group. No significant correlation was found between PLR and neurocognitive test scores.Conclusion: This study revealed negative correlation between NLR and Stroop interference scores. We need further prospective studies with larger sample size to investigate role of inflammation on cognitive functions.