The aim of this study was to evaluate the immediate effect of inhaling racemic adrenaline to treat croup and to evaluate a scoring system. Two groups were investigated. One group inhaled a racemic adrenaline solution and the other group received the same solution with no racemic adrenaline. The study was double-blinded and placebo-controlled. Fifty-four children (0.4-10.8 years) with mild to moderately severe croup were included in the study after clinical evaluation. The clinical score was useful when evaluating the treatment effects in mild to moderately severe croup and may be used as a quality assurance tool when treatment protocols are re-evaluated. Oxygen saturation before and after treatment did not change significantly in either group and therefore its measurement did not provide additional information on the effect of treatment. In both groups, a significant improvement in total mean clinical scores was seen 30 min after inhalation, compared with before inhalation (p < 0.001). However, racemic adrenaline was significantly better than placebo in terms of improvement in total clinical score, inspiratory stridor, retractions and air entry, and should therefore be used as first-line treatment.