Longitarsus Latreille (Chrysomelidae, Galerucinae, Alticini) is a very large genus of phytophagous insects, with more than 700 species distributed in all zoogeographical regions. Patterns of host use have been a central topic in phytophagous insect research. In this study a first assessment is provided to test the hypothesis that host-plant association is phylogenetically conserved in Western Palaearctic Longitarsus species. Maximum Likelihood and Bayesian Inference methods were used to infer a phylogeny based on DNA sequence data from two mitochondrial genes from 52 Longitarsus species from the Western Palaearctic. In agreement with the host phylogenetic conservatism hypothesis, a strict association between most of the recovered clades and specific plant families was found, except for species associated with Boraginaceae. Low phylogenetic resolution at deep nodes limited the evaluation of whether closely related Longitarsus clades are associated with the same plant family or to closely related plant families.