Clinical efficacy of breath actuated devices depend on value of Peak Inspiratory Flow (PIF), in consequence they are used in older children. Therefore the aim of our study was to assess the ability to use breath actuated inhalers in preschool stable asthmatic children. 156 children aged (mean and 95% CI) 4.5 (95% CI: 4.3-4.6) years participated in the study. Peak Inspiratory Flow Rate (PIFR) assessment with In Check (Clement Clark, U.K.) with resistance valve for Turbuhaler, Diskus, Easi Breathe devices was assessed. Minimal effective value of PIFR significantly frequent for Easi Breathe--98.1% (95% CI 94.5-99.4) compared with Diskus--78.2% (95% CI: 71.1-84.0) and Turbuhaler--71.8% (95% CI 64.3-78.3) (p < 0.05) was found. Significant correlation between PIFR and age of children for all devices was confirmed. We conclude that the use of breath actuated Easi Breathe devices seems to be effective in most preschool asthmatic children in stable period of disease. Use of dry powder inhalers should be preceded by assessments of PIFR with In Check.