Abstract. New morphological techniques allow for the evaluation of novel character systems that are potentially important for phylogenetic analysis. Only a few studies so far have used character systems from the insect thorax for phylogenetics; the reasons for this might include a lack of common terminology or established homology for pterygote insect thorax musculature. Still, recent studies have proposed common terminology and hypotheses of homology, now allowing for an evaluation of thoracic morphological character systems among the groups of winged insects. Using X-ray microtomography ( CT) we present a detailed study of the thorax musculature of Odonata as an important phylogenetic character system, with a matrix of 298 characters with 697 character states, including novel data from the thoracic anatomy of eight damselfly larvae. We also included additional Odonata, Ephemeroptera and Neoptera taxa from the literature and demonstrate the phylogenetic relevance of this character system by reproducing phylogenetic topologies of established relationships. We also compared high-resolution data from Odonata larvae from our study and from recent literature with data from older literature in the adult Odonata. All major clades were successfully recovered, (e.g. Odonata, Epiprocta, Anisoptera and Zygoptera) with high node support, but obtained higher phylogenetic resolution with the larval data. The best phylogenetic resolution was achieved by combining the adult and larval characters. The taxon sampling and character matrix is the largest to date and underlines the potential relevance of the thorax musculature as an important phylogenetic character system.