We evaluated influenza vaccination coverage in children with chronic disease at high risk of influenza complications, and the need for methods to increase parents' and pediatricians' knowledge of influenza and its prevention. The 5286 children aged less than 14 years attending our Emergency Department on Wednesdays and Sundays between 1 January and 30 April 2003 included 274 (5.2%) high-risk patients. The use of influenza vaccine during the previous three seasons had been very low, but significantly increased in the last season (2000-2001, 5.1%; 2001-2002, 12.9%; 2002-2003, 26.3%; p<0.001). The children with asthma or cardiac disease showed the lowest vaccination rates; their parents and primary care pediatricians had only a marginal knowledge of influenza and the benefits of its prevention. In conclusion, the delivery of influenza vaccine to children with chronic disease at high risk of influenza complications is completely inadequate, and major efforts are urgently needed to increase parents' and pediatricians' knowledge of its importance.