e18715 Background: Pts with hem diseases are at high risk of COVID-19 severe course and mortality. Emerging data on risk factors and outcomes in this patient population is of great value for developing strategies of medical care. Methods: CHRONOS19 is an ongoing nationwide observational cohort study of adult (≥18 y) pts with hem disease (both malignant and non-malignant) and lab-confirmed or suspected (clinical symptoms and/or CT) COVID-19. Primary objective was to evaluate treatment outcomes. Primary endpoint was 30-day all-cause mortality. Long-term follow-up was performed at 90 and 180 days. Data from 14 centers was collected on a web platform and managed in a deidentified manner. Results: As of data cutoff on January 27, 2021, 575 pts were included in the registry, 486 of them eligible for primary endpoint assessment, n(%): M/F 243(50%)/243(50%), median age 56 [18-90], malignant disease in 452(93%) pts, induction phase/R/R/remission 160(33%)/120(25%)/206(42%). MTA in 93(19%) pts, 158(33%) were transfusion dependent, comorbidities in 278(57%) pts. Complications in 335(69%) pts: pneumonia (67%), CRS (8%), ARDS (7%), sepsis (6%). One-third of pts had severe COVID-19, 25% were admitted to ICU, 20% required mechanical ventilation. All-cause mortality at 30 days – 17%; 80% due to COVID-19 complications. At 90 days, there were 14 new deaths: 6 (43%) due to hem disease progression. Risk factors significantly associated with OS are listed in Tab 1. In multivariate analysis – ICU+mechanical ventilation, HR, 53.3 (29.1-97.8). Acute leukemias were associated with higher risk of death, HR, 2.40 (1.28-4.51), less aggressive diseases (CML, CLL, MM, non-malignant) – with lower risk of death, HR, 0.54 (0.37-0.80). No association between time of COVID-19 diagnosis (Apr-Aug vs. Sep-Jan) and risk of death. COVID-19 affected treatment of hem disease in 65% of pts, 58% experienced treatment delay for a median of 4[1-10] weeks. Relapse rate on Day 30 and 90 – 4%, disease progression on Day 90 detected in 13(7%) pts; 180-day data was not mature at the time of analysis. Several cases of COVID-19 re-infection were described. Conclusions: Thirty-day all-cause mortality in pts with hem disease was higher than in general population with COVID-19. Longer-term follow-up (180 days) for hem disease outcomes and OS will be presented. [Table: see text]