Phylogenetic knowledge in Psylloidea is still very poor, while recent taxonomic and systematic studies have enhanced substantially the classification of the superfamily. This situation is due to either sampling inadequacy or to methodological shortcomings. The present lack of well-supported phylogenetic framework prevents any test of evolutionary scenario. However, close relationships between psyllids and their host-plants, or geographical distribution, make psyllids of special interest in evolutionary biology. First, history and state of knowledge in psyllids phylogeny is given. Then, phylogenetic relationships will be presented based on complete sequences of the 18S rRNA gene for 48 species belonging to 34 genera, covering 11 subfamilies and all of the 6 recognized families. Special attention is paid on alignment of nucleotides, especially in variable regions of the gene, where secondary structures of the molecule are used as a frame in inferring homology. Phylogenetic relationships at this high taxonomic level, as well as evolutionary trends, are discussed.