Introduction: Acute bronchiolitis is a common reason for admission to the pediatric emergency department. Evidence has shown that most interventions do not change the natural course of the disease. Material and methods: This study aimed to evaluate the economic impact of the noncompliance with the acute bronchiolitis Portuguese national guideline. A retrospective study of pediatric emergency episodes of a Portuguese hospital that had a diagnosis of acute bronchiolitis during 2019, was conducted. Results: The sample included 344 emergency episodes. Non-compliance with the guideline occurred in 71.8% of the episodes, mostly due to unjustified treatment. Following guideline in the studied hospital for one year would have resulted in an estimated overall 76.6% cost reduction, with a reduction in mean direct costs per patient of 14.93 <euro>, corresponding to a medium saving of 3.89 <euro> for each patient and a reduction of 11.03 <euro> for the Portuguese National Health Service. Analyzing the unjustified mean direct costs, of these 2.97 <euro> were related to inpatient diagnostic tests and therapeutic and the remaining 11.96 <euro> were related to outpatient therapy. Mean direct costs imputed to the patient for outpatient treatment represented only 3.31 <euro>, therefore most of mean direct costs is paid by the National Health Service. Conclusions: Compliance with guideline would allow the reduction of total estimated costs by about 76.6%, representing a waste of resources, without compromising the quality of care provided. Most of the cost associated with non-compliance with the guideline is justified by outpatient therapy, 67% of which was paid by the National Health Service. (c) 2024 FECA. Published by Elsevier Espana, S.L.U. All rights are reserved, including those for text and data mining, AI training, and similar technologies.