Cardiac troponin T determination plays a dominant role in diagnosis of myocardial pathologies. Despite generally accepted use of high-sensitive cardiac troponin T assays (hscTnT) and clearly defined cut-off limit in adults, the uncertainty persists in infants. The aim of this study was to assess plasmatic concentrations of hscTnT and describe sequential age-related dynamic changes of hscTnT in healthy infants and toddlers. Seventy-eight children (52 males/26 females) from Czech Republic aged 44 to 872 days (median, interquartile range 271; 126 to 486 days) were consecutively enrolled in the single-center, prospective observational study. Plasma concentrations of hscTnT were analyzed by the electrochemiluminescent method, age-related reference intervals were calculated using the polynominal regression model. Amongst the study population (n=78), the upper limit of hscTnT concentration defined as the 99th percentile was calculated. The 99th percentile with 95 % confidence interval at the end of 2nd, 3rd, 4th, 5th, 6th and 7th month of postnatal life were: 81 (40.6 to 63.6), 61 (36.0 to 55.3), 47 (31.9 to 48.3), 37 (28.1 to 42.3), 30 (24.7 to 37.2) and 25 (21.5 to 32.7) ng/l, respectively. Concentration of adults 99th percentile (14 ng/l) was achieved approximately at 1 year of postnatal life. Statistically significant negative correlation of hscTnT concentration with age (r=-0.81, p<0.001) was found. Significant gender differences were not found (p>0.07). The study revealed substantially increased reference intervals of hscTnT levels in infants when compared with adult population. Based on our preliminary results, the age-related interpretation of hscTnT plasmatic concentration is recommended.