Introduction: Trace elements deficiencies are reported in dialysis patients. We aimed to define the frequency of Selenium deficiency in dialysis patients and its correlation with age, gender, duration of dialysis, dialysis modality, and serum levels of blood urea nitrogen (BUN), albumin, total cholesterol and hemoglobin. Materials and methods: Patients under dialysis in dialysis sections of Dr. Sheikh hospital from April 2017 to April 2019 were enrolled the study after taking written consent from patients or their parents. Blood samples were obtained for measurement of serum Selenium levels at time of routine monthly sampling. Results: Forty patients enrolled the study. Totally 45% were under hemodialysis and 55% peritoneal dialysis. The ages in first and second groups were 12. 77±, 2. 94 and 9. 34 ±, 4. 03 years, respectively (P= 0. 04). Serum selenium levels in hemodialysis and peritoneal dialysis patients were 91. 95 ±, 8. 43 and 94. 1 ±,8. 67 microgram (µ, gr) per liter, respectively (P= 0. 374). Thirteen cases (32. 5%) including 38. 9% of hemodialysis and 27. 3% of peritoneal dialysis patients had Selenium deficiency (P= 0. 435). No correlation were found between age, gender, modality of dialysis, dialysis duration, serum levels of BUN, albumin, total cholesterol and hemoglobin with Selenium deficiency (P> 0. 05 for all ). Conclusion: Selenium deficiency is common in dialysis patients. Demographic factors, dialysis modality, dialysis duration, serum levels of BUN, albumin, total cholesterol and hemoglobin are not related with presence of Selenium deficiency. Periodic checking of serum levels of Selenium is recommended.