BACKGROUND: Cytomegalovirus (CMV) is endemic worldwide, with marked differences in the seroprevalence rates between countries. The aim of this study was to analyze the seroprevalence of CMV infections in Croatia. METHODS: During a 3-year period (2013-2015) 2438 consecutive serum samples collected from Croatian residents were tested for the presence of CMV IgM and IgG antibodies using enzyme- linked immunoassay. The IgM/IgG positive samples were further tested for IgG avidity. RESULTS: The overall seroprevalence rates for CMV IgG and IgM antibodies were 74.4 % and 4.3 %, respectively. The IgG seroprevalence showed significant differences between population groups: children/adolescents 54.6 %, general adult population 77.2 %, hemodialysis patients 91.4 % (p < 0.001). Seropositivity of CMV was strongly age-dependent with prevalences ranging from 53.0 % in children less than 10 years old to 93.8 % in persons above 60 years (p < 0.001). There was no difference in the prevalence rate between women with normal pregnancy and women with poor obstetric history. Gender and place of residence were not associated with CMV seropositivity. Using IgG avidity, current/recent primary CMV infection was confirmed by a low/borderline avidity index (AI) in 46.7 % participants, while in 53.3 % a high AI indicated CMV reactivation or reinfection. Primary infections were detected mainly in children and adolescents (83.2 % and 70.5 %, respectively), while reactivation/reinfection was common in persons older than 40 (77.0-100 %). Reactivation/reinfection was most commonly detected in hemodialysis patients (92.3 %). Logistic regression showed that older age and being on hemodialysis were significant predictors of CMV seropositivity. CONCLUSION: Infections with CMV are widespread in the Croatian population. Older age and being on hemodialysis appear to be the main risk factors for CMV infection.