We have compared the biodiversity variations in moth communities between unmanaged forests and commercial forests in a mountainous environment (Pyrenees France). The aim was to evaluate the impact of forestry activities on moth diversity. The data collected from the insects were analysed with a Bayesian specific similarity index (noted SSP index) and by statistical biodiversity indexes comparison. It was seen that diversity and richness were decreased in the plantation compared to the unmanaged forest. Interestingly,the composition of the communities of moths was shown to be not only related to the presence/absence of host plants, but also to be in relation with changes in the differences in forest architecture (i.e. the relative coverage by the different vegetation levels). However, the moth community in the commercial forest still has a high capacity to converge with the moth community present in more natural forests. We report here a list of 177 species of moths,providing information on the distribution of some uncommon species, poorly studied as yet in the Pyrenees.