The prevalence of insomnia is greater in end-stage renal disease. The aim of our study was to determine the frequency of insomnia and subclinical insomnia in patients with various dialysis therapy and kidney transplant recipients, in order to assess the severity of insomnia and examine whether there is a difference in severity among groups. In cross-sectional study, we evaluated 120 patients with terminal renal failure. Based on therapy, patients were divided into four groups: hemodiafiltration, standard bicarbonate dialysis, peritoneal dialysis and kidney transplant recipients. The severity of insomnia was evaluated through the use of the Insomnia Severity Index (ISI). Most patients who reported any kind of insomnia problems with ISI were on conventional dialysis (80%), followed by hemodiafiltration (76.7%) and peritoneal dialysis (63.3%). Transplant recipients had least difficulties with insomnia (46.7%). Insomnia Severity Index showed that insomnia in end-stage renal patients is not very severe. Most of the patients had “no clinically significant insomnia”. Our findings indicate that patients on hemodiafiltration and transplant recipients have a significantly lower score on Insomnia Severity Index. Patients with end-stage renal disease have high frequency insomnia problems. However, our study shows that insomnia in these patients is not severe. Insomnia is the most frequent and severest in patients on standard bicarbonate dialysis.