Background and aim: Postural orthostatic tachycardia syndrome (POTS) is one of the most common types of dysautonomia and orthostatic intolerance that has a negative effect on quality of life. Main clinical criterion for diagnosis is an increase in heart rate (HR) >30bpm while standing for >10 minutes and the absence of orthostatic hypotension. The aim of the study was to determine the differences in nonstandard adrenergic baroreflex sensitivity indices between POTS patients and healthy controls. ----- Methods: This study included 39 POTS patients and 51 healthy controls. Baroreflex sensitivity indices were calculated via retrosopective analysis of systolic blood pressure curves during the Valsalva manuever (VM) and then compared between the groups. The curves were further divided into three groups: BAR (basic adrenergic response), SAR (supressed adrenergic response) and AAR (augmented adrenergic response) and analysed. In POTS patients, levels of catecholamine were measured during the tilt-up test and correlation was established with α-BRSa, β-BRSa or BRSa1 indices. ----- Results: The results have shown that there was a significant difference in the α-BRSa index between the groups (p=0.004). In the POTS group there was a difference in noradrenaline levels found between hyperadrenergic type and non-hyperadrenergic type in both positions during tilt-up test: supine (2.152±0.949 versus 1.139±0.501; p=0.006) and standing (5.140±1.731 versus 2.600±0.511; p=0.001). The difference in the BRSa1 index between H and non-H groups was also detected (18.42±13.40 versus 33.13±20.59 p=0.04). Furthermore, a connection was drawn between indices, types of curves and catecholamine levels in the POTS group. ----- Conclusion: This research shows that there is a significant difference in the α-BRSa index, which is most likely due to irregular hemodynamic response to the VM as a result of a dysfunction in the autonomic nervous system. The increased levels of catecholamine can also explain why patients with hyperadrenergic type of POTS experience such exaggerated symptoms of sympathetic hyperstimulation.