BACKGROUND: Deferred blood donors are not targeted by any health policy. OBJECTIVES: To describe sociodemographic characteristics of unsuitable blood donors, the causes of unsuitability and compare the prevalence rates of transfusion-transmitted infections in deferred and eligible blood donors. METHODS: A cross-sectional survey was conducted to obtain sociodemographic data and blood samples; 8,159 donors were screened; (21.1% rejected, 78.9% approved). A sample of 212 deferred donors was established. RESULTS: Most rejected donors were female, young adults, with high school or university education, self-declared white, born in the North region and single. Main reasons for unsuitability were low hemoglobin concentration, potential exposure to malaria and risky sexual behaviour. The comparison of seropositivity rates in deferred and eligible blood donors generated the following prevalence ratios (PR) and respective 95% confidence intervals (CI): HIV, PR = 6.75 (1.46 – 31.05), p = 0.046; syphilis, PR = 1.47 (0.46 – 4.64), p = 0.463; anti-HBc, PR = 2.84 (1.24 – 6.50); p = 0.023; anti-HCV, PR = 4.67 (1.06 - 20.58), p=0,080; Chagas disease, PR = 60.75 (5.53 – 667.43), p = 0.003. CONCLUSIONS: Treating anemia in women and controlling malaria in Roraima will reduce the pool of rejected donors in the state.