Introduction: Pheochromocytoma is a tumor of the chromaffin cells of the adrenal gland. It is characterized by the over-synthesis and excretion of catecholamines and their metabolites, which in turn leads to hypertension, tachycardia, increased sweating, palpitations, severe headaches and pallor. The diagnosis of pheochromocytoma is based on clinical picture, biochemical tests for determination concentrations of metanephrine and normetanephrine in plasma and daily urine and as confirmatory methods are used imaging radiological techniques (CT, MRI). HPLC-ECD or LC-MS/MS are the methods of choice for the determination of plasma metanephrine and normetanephrine, while HPLC is considered the reference method for the measurement of catecholamines and their metabolites in daily urine. Goals: To investigate the accuracy of metanephrines in plasma and daily urine and optimize the diagnosis of pheochromocytma. Materials and methods: A retrospective case-control study was conducted. Existing results of measurements of metanephrine and normetanephrine concetrations in plasma and daily urine from the Laboratory Information System have been retrieved as well as imaging data from the Hospital Information System. ROC analysis and post hoc Kruskal Wallis Dunn test have been performed. Results: ROC analysis showed the sensitivity of the method for measuring methanephrine in plasma and daily urine of 80%, and sensitivity for normetanephrine in plasma and dauly urine of 100%. The specificity for plasma methanephrine and daily urine is 100%, and 92.08% for plasma normethanephrine and daily urine. Post hoc Kruskal Wallis Dunn test showed that, unlike metanephrine, normetanephrine distinguishes pheochromocytoma from other diseases.Conclusion: There are no statistically significant differences in the diagnostic properties of the plasma and urine indicators of pheochromocytoma, but analyzes of normetanephrine in plasma and 24-hour urine have slightly better diagnostic properties.