BACKGROUND: The aim of the work is to define the morphological peculiarities of the autonomic nervous system (ANS) in the thoracic region. MATERIAL AND METHODS: An anatomical study was performed on 20 cadavers, 17 men and 3 women. We studied cadavers within 24 h of death. We observed the vertebral and prevertebral section of the truncus sympathicus, their morphological peculiarities depending on the type of ANS. To show the intimate relationship of both systems, we also focused on the details of the structure related to the connections of the ANS with the spinal nervous system. RESULTS: In the thoracic region, the segmental arrangement of the truncus sympathicus ganglia prevailed in 16 (80%) cases. Rami communicantes gave anastomoses to spinal nerves. Small ganglia were observed on the rami communicantes to the spinal nerves. In the case of the concentrated type, in 4 cases (20%), we observed a reduction in the number of ganglia, as well as the absence of small ganglia on the connecting branches. Connections between n. vagus and sympathetic branches were poorly developed. We observed right-left asymmetry and differences in the formation of ganglia and anastomoses in the truncus sympathicus in the vertebral and prevertebral section. Variations of distance of n. splanchnicus major were observed in 16 cases (80%). CONCLUSION: This study allowed us to identify and describe the morphological peculiarities of the thoracic ANS. The variations were numerous; their preoperative diagnosis is difficult to impossible. The knowledge gained can be helpful in clarifying clinical signs and symptoms.