Although guideline-based asthma care and adherence to inhaled corticosteroids are predictors of asthma control, the role of adherence in maintaining long-term asthma control is largely unknown. This study was designed to explore the relationship between adherence to inhaled corticosteroids and long-term asthma control in young children with asthma. In this observational study, 81 2-6-year-old asthmatic children, using inhaled corticosteroids, closely followed-up in a programme with extensive self-management training, were enrolled. Adherence was measured daily for 12 months using Smartinhaler (Nexus6 Ltd, Auckland, New Zealand) devices. Long-term asthma control was assessed by parents and physicians and included clinical assessment, an asthma control questionnaire and lung function measurement. We examined the association of adherence to asthma control, adjusting for seasonal influences and clinical characteristics. Median (interquartile range) adherence was 87% (70-94%), and 64 (79%) children had well-controlled asthma throughout follow-up. Adherence >80% was associated with better asthma control, and we found no important confounders of this association. Children with persistent mild symptoms had lower adherence rates (p=0.028). Guideline-based asthma care was associated with good asthma control in most children. Adherence to inhaled corticosteroids was an independent strong predictor of long-term asthma control, with highest levels of asthma control found in children with adherence >80% of doses prescribed.