Background <p>The role of the government in providing health insurance for the population is to ensure that everyone has access to affordable and quality healthcare services. According to previous studies, health insurance generally has a positive impact on access to healthcare services and health outcomes; however, evidence from developing countries is lacking.</p> Methods <p>Using a regression discontinuity design that exploits discontinuities in eligibility for the program, we analysis the effects of the Peruvian comprehensive health insurance program on the use of medical services. To check whether the impacts are heterogeneous across subpopulation, we consider subsamples by age, educational attainment and place of residence.</p> Results <p>Those with public health insurance use healthcare service more often, largely due to a wider range of general care. More importantly, we found that the impact of health insurance is greater among people with lower education and older adults. The impact of the use of medical services was statistically significant only in urban areas.</p> Conclusions <p>These findings suggest that increased public health-insurance coverage may help reduce disparities in health and that more investment in healthcare resources in rural areas is needed to further alleviate these disparities.</p>