BACKGROUND: It has been suggested that alcohol consumption is associated with increased risk of a few solid cancers, although studies that examined the association with hematological malignancies have shown inconsistent results. In this study, we examined the risk of hematological malignancies among individuals who had alcohol use disorders (AUDs) in Sweden. METHODS: Individuals with AUDs were identified from the nationwide Swedish Hospital Discharge Register and Outpatient Register, the Crime Register, and the Prescription Drug Register, and they were linked to the Swedish Cancer Registry to calculate standardized incidence ratios (SIRs) of hematological malignancies, using those Swedes without AUDs as a reference. In addition, we used a quasi-experimental sibling design to investigate the odds ratios among sibling pairs who were discordant with AUDs. RESULTS: A total of 420,489 individuals were identified with AUDs. After more than 15 million person-years of follow-up, a total of 1755 individuals developed hematological malignancies demonstrating a low risk, i.e., SIR = 0.60 (95% confidence interval = 0.57-0.63). People with AUDs had low risks for developing specific types of malignancies. The lowest risk (0.51) was for leukemia, followed by myeloma (0.52), non-Hodgkin lymphoma (0.65), and Hodgkin disease (0.71). The risk was lower among AUDs identified at an older age. The low risks of hematological malignancies were also noted using sibling analysis. CONCLUSIONS: Our data suggest that alcohol consumption has a protective effect against hematological malignancies. However, further studies are needed to identity the underlying mechanisms of the protective effect of alcohol consumption against hematological malignancies.