INTRODUCTION: Infantile hemangiomas (IH) are the most common benign vascular tumors of childhood, with an incidence of 5-10% during the first year of age. Propranolol is considered the first-line treatment for this condition. Potentially there is a high probability of negative results to therapy, because in many countries there are no treatment protocols or propranolol formulations appropriate for the pediatric population. The objective of the present study was to evaluate the impact of pharmacist interventions such as detecting, analyzing, and solving problems presented during treatment with propranolol in patients with IH. METHODS: An open observational prospective study was performed over 25 months in a group of pediatric patients diagnosed with infantile hemangioma treated with propranolol. Pharmacist participation consisted of development of an extemporaneous formulation and counseling the child's parents. At each visit to the pharmacy service, family members were interviewed, detecting and classifying problems related to treatment. RESULTS: Sixty-three children with IH were treated during the period under review. Patient ages ranged from 3 to 11 months old; 64% were female and 36% were male. Forty-nine problems in 30 patients were detected, principally inadequate dose (18.4%), non-adherence to treatment (16.3%), side effects (14.3%), and wrong administration (14.3%). Of the problems detected, 81.6% were resolved. Interventions by the pharmacist in 27 patients were intensive counseling on adherence to therapy (20%), detection of adverse effects (11.4%), and adjustment of the dose (22.9%). In 95.2% of patients a good response to treatment was obtained compared with 77.2% reported in European studies without pharmacist intervention. CONCLUSION: It seems that pharmacist participation increases adherence to treatment and reduces the likelihood of adverse effects, allowing for safe and effective therapy in patients with IH.