WHAT IS KNOWN AND OBJECTIVE: Diabetes mellitus (DM) is major cause of death and disability, and regular administration of medications is important in its management. A better understanding of the factors associated with medication non-adherence or underuse may help to improve adherence. This study was performed to identify and compare possible risk factors associated with medication adherence to antidiabetic medication in two different community-based populations in Korea. METHODS: In this large, cross-sectional study, data on DM patients from the rural area of Ansung and the urban area of Ansan obtained during biennial health examinations in 2011-2012 were analysed. Demographic information and anthropometric and laboratory test results were collected. The study population consisted of rural and urban communities which were each categorized into two groups according to medication adherence: those who were currently on antidiabetic medication (adherent group), and those who did not take the medication despite knowing that they are diabetic (non-adherent group). RESULTS AND DISCUSSION: A total of 1675 inhabitants who were diagnosed as diabetic were included in this study comprised of 803 patients from the rural community and 872 patients from the urban community. Over half of the study population (55.76%, 934 patients) belonged to the non-adherent group. Adherence was greater in the rural (52.43%) than in the urban (36.70%) group. There were significant associations between medication non-adherence and age, male gender, alcohol consumption, high blood pressure, high total cholesterol and lack of family history of diabetes, but not with income, smoking status, exercise, marital status and occupation. WHAT IS NEW AND CONCLUSION: Despite the proven beneficial effects of antidiabetic medications in the management of DM, we observed low rates of medication adherence, particularly in the urban area. Further study to identify barriers to adherence among urban residents is needed. In addition, there is a need for effective strategies that will lead to improved medication adherence.