OBJECTIVES: Hypertension is endemic in Hungary today. Incorrect measuring tool of blood pressure can be responsible for hypertonia diagnosed improperly. Our goal was to examine differences between values measured with different tools. METHODS: Our survey was a quantitative, cross-sectional study in the Kaposi Mór Teaching Hospital Outpatient care unit, Somogy County, Hungary in 2016. Non-randomized, purposive sampling was used to enroll patients between 18-85 years of age. (N=201). Exclusion criteria were: pregnancy, injured, amputated, paralyzed, fractured arm, having lymphoedema, contracture, chimino fistule, midline iv. catheter or other that can hinder correct measuring on the upper arm. We used mercurial, aneroid, oscillometric, patient-monitor attached blood pressure meters. Descriptive and mathematical statistics (t-test, chi-square test, ANOVA) were made on MS Excel software (p<0.05) RESULTS:  ANOVA statistics approved significant difference between systolic and diastolic parameters measured by different tools.(p<0.05) Post-hoc analysis showed significant difference between systolic values measured by mercurial and monitor-attached, and aneroid and monitor-attached oscillometric measuring (p<0.05). From the aspect of the diastolic values, we found significant differences between mercurial and monitor/oscillometric device. There is also a significant difference between the aneroid and monitor/oscillometric measuring. (p<0.05) CONCLUSIONS: We can consider mercurial and aneroid blood pressure meters accurate, the monitor- and oscillometric devices recorded higher blood pressure rates. It is important – especially in patients with hypertension – to control the blood pressure with validated measurement tools in the everyday practice.