The term "effectiveness" relates to the question of whether or not a certain treatment works in practice. Usually, such a treatment was first evaluated under tightly controlled conditions in selected patient populations, and the potential benefits were shown. There is, however, a great difference between the efficacy of a given treatment, indicating its optimal therapeutic action in controlled trials, and its effectiveness when applied to a less well-defined population of patients in daily practice. This is especially relevant for asthma in young children, where many factors are responsible for the difference. Among these are, first of all, the heterogeneity of the wheezing phenotype. Other factors include the compliance with prescribed treatments, as determined by the attitude of doctors and parents towards such treatment, the ease of administration and the perceived effects and side effects. Also, the performance of different inhaler devices may be insufficient for a good, reliable dose deposition in young children in daily life. As a result, the current treatment guidelines for preschool children with recurrent wheeze are probably too optimistic in assuming that inhaled treatment is most effective and feasible at all ages. We propose careful re-evaluation of such recommendations in a first-line setting resembling daily life as closely as possible, and consideration of oral treatments as well. Also, we need methods to separate the different phenotypes within the group of recurrently wheezing preschool children to optimize targeting of asthma treatment to those who have ongoing airway inflammation.