This multi centre observational cohort study gives a view about the occurrence, clinical and laboratory presentation, localization, histological type and genetic background of pheochromocytoma (PHEO) and paraganglioma (PGL) in Eastern Slovakia. It included 28 patients (18 women + 10 men), of which 23 were diagnosed to have PHEO (82,1%) and 7 patients (25%) suffered from PGL with retroperitoneal, inguinal/pelvic and mediastinal distribution. Arterial hypertension was the major symptom present in 86 % with slight dominance of paroxysmal form (58%). In 3 cases (10,7%), the diagnosis was gained after differentiation of adrenal incidentaloma in asymptomatic patients. Five patients (17,8%) were classified to have malignant form of the disease. 9 patients (32,1%) were confirmed to have hereditary form - five of them (17,8%) with familiar medullar thyroid cancer (FMTC) and mutations in RET gene classified as multiple endocrine neoplasia 2A and 4 patients (14,3%) with germline mutations of SDHB gene, respectively. There was found a relatively high occurrence of other co-morbidities: thyroid disease in 20 patients (71,4%), impairment of glucose metabolism in 11 patients (39,3%) and apart from FMTC, 4 patients (14,3%) suffered also from other malignancy. Together with a bigger size of the primary tumor (6,6 cm), higher concentrations of metanephrines and prevalence of extra-adrenal tumors, malignant and hereditary forms, we suppose genetic and environmental factors of Eastern Slovakia may play a role in the etiopathogenesis of the tumors.