The aim of this study was to examine the relation between the public perceptions and reactions to the pandemic influenza A(H1N1) in Crete, Greece. It was conducted in two phases: at the early phase of the outbreak and during the peak. The Common Sense Model was used as an appropriate theoretical framework. Participants were 273 healthy adults. Perceptions, especially perceived control and emotions, were related to protective behaviours, infection management behaviours and detachment at both phases of the study and also predicted follow-up reactions. Moreover, emotions predicted changes in behaviour and moderated the effects of several perceptions on pandemic-related behaviour.