The area configuration of healthcare resources, such as the number of hospitals per hundred thousand population, has often been used in healthcare planning and policy making to estimate the global access (potential access) of health services to a local population. However, the actual utilization of the "available" healthcare resources (revealed access) is usually much more limited. The objectives of this study were to examine the availability of healthcare resources by measuring the potential access and the revealed access for outpatients who need to access pharmacies to fill prescriptions of Schedule II (CII) opioids for pain management, and to explore the difference between rural and urban residents in these two types of access. About 191,700 prescriptions for CII opioids dispensed in 1997 in the state of Michigan, USA were analyzed. Revealed accessibility was measured by the distance between the paired zip codes of the pharmacy and the patient listed on each prescription. Potential accessibility was measured by the distance from a patient's zip code to that of the nearest community pharmacy that could dispense the opioid prescriptions. The analyses on revealed access showed that 50% of the CII prescriptions were dispensed by pharmacies located within a 5-mile radius of patients' residences, 75% of prescriptions were dispensed within about a 10-mile radius, and 90% were within 20 miles. If patients were free to access the nearest pharmacy for dispensing (a hypothetical situation under potential access), the median, 75th percentile, and 90th percentile distances could reduce to 2, 3, and 5 miles, respectively. Similar differences between revealed and potential access were observed in both rural and urban areas and for every major opioid drug group. We conclude that policymakers should recognize the discrepancy between potential and revealed accessibility and move beyond only considering area configuration of healthcare resources to evaluating and improving access to care.