Objectives: Reference values are fundamental for the interpretation of laboratory results, which are useful for medical decisions. Each laboratory has to have its own reference values classified according to age groups in order to interpret test results correctly. The expression “normal values” has been replaced by “reference values” because there are various variables that are considered to influence these values. The majority of “reference values” were established over two decades ago using obsolete medical devices and in many cases undefined populations; therefore, nowadays these intervals are not relevant anymore for modern testing technology in clinic laboratories. Methods and materials: The study was carried out at Sibiu Clinic Pediatric Hospital using the laboratory’s electronic archive. The samples were taken from hospitalized patients (children and teenagers) and outpatients registered between January and December, 2010. Blood sample testing was performed using the Sysmex XS 1000i analyzer. The reference values for hemoglobin was calculated based on results from a population sample of 9838 patients. The patients were classified into 3 age categories: 1 month - 2 years old; 2 - 10 years old; 10 - 18 years old. Reference values were determined after eliminating outliers,using the robust method to calculate 2.5 and 97.5 percentiles with the SPSS statistical software. Results and Conclusions: The results obtained differed from those specified in the Roche Diagnostics 2004 Guide but were found to be close to the results mentioned in Lothar Thomas’s publication, in Laboratory diagnostics.