Respiratory illness and diarrhea are the two most important causes of death in children under the age of 5 in the Philippines. The government has accorded high priority to reducing the number of deaths caused by these illnesses as it attempts to reform its healthcare system. In order to re-design health systems, policy makers need to have a good understanding not only of overall health services utilization, but also of the use of public and private sectors. We used the 1998 Philippines National Demographic and Health Survey dataset to understand the service utilization patterns of children under 5 with diarrhea and/or respiratory illness. Using the Andersen Model as the conceptual framework, a nested logit regression approach was used to determine predictors of health services use, and of public vs. private use in this population. Our results indicate that maternal education and number of illnesses determine the decision to seek care. Once the decision has been made to seek care, the choice between a public or private provider is affected by the family's economic status and size of the household. Policy makers can use such information for future health planning and reform, in order to increase access to healthcare for this vulnerable population in the Philippines.