Background Undiagnosed disease is one of the critical public health problems in the world. In 2002 South Korea introduced the nation's first comprehensive public health promotion policy, Health Plan 2010. The first phase of Health Plan 2010 started in 2002, promoting the early detection of diseases and preventive care and continued until 2005.

Methods Using the 2001 and 2005 Korean National Health and Nutrition Examination Surveys that were fielded before and after the health promotion programme, this study investigated the changes in healthcare utilisation and its impacts on the prevalence of diagnosed and undiagnosed diabetes as well as good management of the disease.

Results A significant increase in diabetes diagnoses has occurred during this time period, especially for those with low education and older age. It was found that, during this time period, the prevalence of undiagnosed diabetes was significantly reduced especially among older and less-educated Koreans, the principal targets of the programme. This health promotion was also found to have had significant positive effects on the good management of diabetes.

Conclusions The increase in preventive health care through medical check-ups among less-educated, older people suggests that the implementation of free medical check-ups for individual aged 40 years and older may have a positive impact on those who had not previously used preventive care. The positive experience in South Korea indicates that similarly designed public health campaigns in other countries have enormous potential for improving the detection and management of chronic disease.