We estimated cost-effectiveness of annually vaccinating children not at high risk with inactivated influenza vaccine (IIV) to range from US $12,000 per quality-adjusted life year (QALY) saved for children ages 6-23 months to $119,000 per QALY saved for children ages 12-17 years. For children at high risk (preexisting medical conditions) ages 6-35 months, vaccination with IIV was cost saving. For children at high risk ages 3-17 years, vaccination cost $1,000-$10,000 per QALY. Among children notat high risk ages 5-17 years, live, attenuated influenza vaccine had a similar cost-effectiveness as IIV. Risk status was more important than age in determining the economic effects of annual vaccination, and vaccination was less cost-effective as the child's age increased. Thus, routine vaccination of all children is likely less cost-effective than vaccination of all children ages 6-23 months plus all other children at high risk.