Background: Sufficient preoxygenation prevents arterial oxygen desaturation prior to intubation. An optimally sealed facemask is necessary for fast preoxygenation.Aim: to compare the efficiency of preoxygenation using two different facemasks. Materials and methods:In 2018 a prospective study was conducted. Patients were classified into groups: Group A -Intersurgical Economy facemasks, Group B -Intersurgical QuadraLite masks. The circuit was flushed with 100% O 2 for 30s, preoxygenation started with flow of 8l/min, FiO 2 100. Patients were asked to breathe deeply. Fentanyl (1-2 mcg/kg) was administered to increase mask toleration. End-tidal oxygen concentration (EtO 2 ) ≥ 90% was the goal. EtO 2 was monitored after 30, 60, 90, 120, 180, 210, 240, 270 and 300 seconds. Data analyzed using Independent-Samples T-test, Mann-Whitney-U test. Results: 12 patients were enrolled in group A and 19 in group B. Differences in gender, age, BMI and Mallampati class in the groups were statistically insignificant (p=0.13, 0.39, 0.65, 0.43 respectively). Patients assigned to ASA I -25.8% (n=8->2/6), ASA II -71.0 % (n=22->10/12), ASA III-3.2% (n=1->0/1), p=0.64. The success rate of preoxygenation to EtO 2 90 within 5 min was statistically significantly different in the groups with 33.3% in group A and 94.7% in group B (p<0.01). Mean time to EtO 2 90 was 228.3 ± 104.0/164.4 ± 84.3. Mean EtO 2 after