Despite being the most common chronic lung disease in children, asthma continues to be frequently misdiagnosed in the pediatric population. The recommendations to establish a diagnosis of asthma in school-aged children have evolved over time, but there are still important discrepancies between published guidelines. Furthermore, preschool-aged children are often unable to perform objective testing, so the diagnosis of asthma remains a clinical one in the first several years of life, and there is still debate on the criteria and nomenclature to be used in this age group. In this review, we first discuss the definition and misdiagnosis of asthma in children. We then assess and compare published guidelines that outline how to establish the diagnosis of asthma in school-aged children. We also discuss the necessary steps to diagnose preschool-aged children with this disease. Last, we outline unanswered questions and opportunities for research in this field.