OBJECTIVES To examine the nature of unmet prescription medication need (UPMN) due to cost, health plan problem and lack of insurance using 2003 National Survey of Children's Health (NSCH). METHODS A nationally representative sample of 102,353 children under 18 years of age from 2003 and 2004 NSCH was used for analysis. Children who did not get all the prescription medication needed in the past twelve months due to cost, health plan problem or lack of insurance were examined. Multivariate logistics models within the conceptual framework of Andersen's Behavioral Model were used to examine the predictors of UPMN due to cost, health plan problem and lack of insurance. RESULTS According to NSCH, 35.39% children did not receive medications due to cost, 26.51 % due to health plan problem, and 40.73% due to lack of insurance. Multivariate logistic regression for UPMN due to cost revealed that children with attention deficit hyperactive disorder (Odds Ratio (OR), 2.39) or asthma (OR, 3.15) were more likely to report UPMN due to cost and children having public insurance (OR, 0.26) or gained insurance (OR, 0.26) were less likely to report UPMN due to cost. Logistic regression model for UPMN due to health plan problem revealed that racial group other than whites and blacks (OR, 4.35), children with public insurance (OR, 11.98) and gained insurance (OR, 2.85) were more likely to report UPMN due to health plan problem. Lastly, children of 5-11 years (OR, 11.18) and 12-17 years (OR, 6.15) were more likely to report UPMN due to lack of insurance. CONCLUSIONS Several predisposing, enabling and need factors are associated with UPMN due to cost, health plan problem and lack of insurance. Findings suggest that there is a need to focus on certain sociodemographic groups to improve access to prescription medication for children.