Background: Antibiotics are among the most common drugs prescribed in outpatient settings. It is estimated that up to 50 % are prescribed unnecessarily or inappropriately. To plan the actions for optimizing the use of antibiotics, we conducted a national antibiotic consumption study in children aged 0–18 years in the period between 2003 and 2015.Methods: In this national retrospective research we analyzed outpatient antibiotic consumption using ATC/DDD classification. The use of antibiotics was recorded in relation to the pattern of prescription, age, gender and health region.Results: The total consumption of antibiotics decreased by 35 % from 979 to 636 prescriptions per 1000 children/year (PTY) during the whole study period. Te use of all antibiotic classes decreased (except for quinolones and nitrofuran derivatives) by 12.5 %–81 %. In all those years we recorded the highest consumption in children aged 1 to 4 years (2184–1160 PTY). Amoxicillin was the most commonly prescribed antibiotic in children aged 0 to 4 years, penicillin V among 5 to 14 years and co-amoxiclav among adolescents aged 15 to 19 years. In health regions in the northeastern part of Slovenia much more antibiotics were prescribed than in other regions. In 2015, 65 % of prescriptions were prescribed by pediatricians and school medicine specialists, 16 % by physicians without specialization, 14 % by GPs/family doctors and 5 % by other specialists.Conclusions: Despite the decrease in outpatient antibiotic use in children and adolescents in Slovenia, the overall and especially broad-spectrum antibiotic consumption (amoxicillin with clavulanic acid, azithromycin and second/third generation cephalosporins) is still too high. It is necessary to strengthen activities to reduce prescribing, particularly for acute (upper) respiratory tract infections.