The ‘Nest Protection Hypothesis’ suggests that some birds add aromatic plants to their nests to repel or kill ectoparasites. This behavior has been described for several species, including the Eurasian Blue Tit (Cyanistes caeruleus). We studied the reproductive performance, based on 26 nests (in nest boxes), of this species in mixed forested areas of Quercus spp. and Pinus pinea in the ‘Parque Florestal de Monsanto’, the largest park of Lisbon, Portugal. The frequency of aromatic plants in nests was compared with frequency of these plants in the study area. The three most frequent aromatic plants (Dittrichia viscosa, Lavandula dentata, Calamintha baetica) in nests were used more than expected from their availability in the study area. We could not reject the null hypothesis that nest survival rate is independent of the presence of aromatic plants in the nest.