Many years on since its introduction Korea’s National Health Insurance (NHI) remains criticized for limiting access to health care and increasing out-of-pocket burdens on households, with its coverage still far below the average of its OECD counterparts (63.4 percent vs. 79.7 percent) even after a couple of mid-term improvement plans. The first mid-term plan (2005~2008) exempted children aged 6 and below from copayment and lowered out-of-pocket costs for people with cancer, heart disease, and cerebrovascular disorder. The second plan (2009~2013) further lowered out-of-pocket costs for the three diseases, included pneumonia and major burn injuries in the copayment reduction program, and set copayment limits that would apply differentially to different income groups. The previous government also has actively sought to expand the range of covered services and increase the target population especially for those with cancer, heart disease, cerebrovascular disorder, and rare and intractable disease. Policies of health coverage expansion are aimed primarily at reducing the financial burden families have in paying for their health care and at ensuring that health services are used equitably as medical needs arise. The fact that the same amount of out-of-pocket copayment may carry different weights for households of different income levels may keep medically necessary services from being used equitably. One way to monitor how equitably health care is provided is by looking at differences in household health expenditures across different income groups. This study examines changes that have occurred over recent years in the out-of-pocket health expenditures of households of different income levels with members having cancer, heart disease, and cerebrovascular disorder, as these are the ones the coverage expansion policy has focused on most in recent years. To better understand if differences in income lead to differences not only in the amount but also in the composition of household health expenditure, this study looks also at household expenditures on inpatient care, outpatient care and prescription medication.